Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Periodic Table
Document related concepts
Transcript
CHAPTER
4.1 METHOD ADOPTED
4.1.1 TOOLS & TECHNIQUES EMPLOYED
FOR THE STUDY
I
4.1.3 EXPERIMENTAL DESIGN &
PROCEDURE
4.1.4 STATISTICAL TECHNIQUES APPLIED
4
I
/<:
i 1,
/L.*
-~
--
~. ..
..
L.,
,,
.
METHODOLOGY
The details regarding the tools and techniques employed.
method or procedure adopted for collecting data and the statistical
techniques employed for the analysis of data are given below:
4.1
METHOD ADOPTED
The Investigator adopted Experimental cum Survey Method
for the present investigation.
The details regarding the method / procedure adopted for
collecting the data are given below under appropriate heads.
4.1.1
TOOLS AND TECHNIQUES EMPLOYED FOR THE
STUDY
The
following
tools
were
employed
for
collecting
necessary data.
(1)
A Two-tier Diagnostic test in Chemistry for Educationally
Backward Students studying in standard IX
(2)
Remedial Teaching Materials in Chemistry for Educationally
Backward Students on the following topics:
(i)
Periodic Table
.
Methodology' . . ' .
Methodolow
(ii)
Atomic Structure
( i ~ i ) Oxidation & Reduction
(3)
Ach~evement test in Chemistry for students studying in
Standard IX (used as pre and post tests)
(4)
Rating Scale for experts and Secondary School Chemistry
Teachers
(5)
Questionnaire for Experts and Secondary School Chemistry
teachers
(6)
General Data Sheet
All the above mentioned tools were prepared by the
Investigator for the present study. The details regarding the tools
used for the present study are given below:
1.
FI'\VO-TIEK DIAGNOSTIC
':ducationally
TEST
IN
CHEMISTRY
(for
Backward Students in Chemistry studying in
Standard IX)
To construct a Diagnostic test, the Chemistry text books
prescribed for Standards VIII. IX and X were thoroughly analysed
and 6 3 learning points under different topics were listed. The list
of learning points was given to experienced teachers and experts
in Chemistry to get their opinion. According to their suggestions
Methodolow
some of the learning points were deleted, some were added and
some were modified. Thus 50 learning points from seven different
topics (Acids and Bases, Atomic Structure, Chemical Bonding,
Language o f Chemistry, Oxidation & Reduction, Periodic
Table, and Physical and Chemical Changes) were selected for
the preparation of Diagnostic Test. (/ T*ble,.S.
+-~>:--.
I
').
On the basis of the teaching points (n = 50), Investigator
prepared a Diagnostic Test having 50 multiple choice items, to
collect details regarding the errors committed by the Educationally
Backward students in Chemistry studying in Standard IX.
The
items for the Diagnostic Test were based on the Two-tier multiple
choice format described by ~ a m i r ' (1971). Tobin and capie2
(1981) and ~ r i ~ u (1986-1987).
s t ~
Each item has two tiers. The
first tler of each item consists of a content question having 4
choices.
The student has to choose the most suitable answer
from the given 4 choices and make a tick mark in the answer
sheet. The second tier of each item contains 4 possible reasons
for the answer given in the first tier of the item. The student has
to choose the most suitable reason for their answers for the first
tier and make a tick mark in the answer sheet provided.
The
answer to an item was considered correct if the student selected
Methodology
.
both the correct content choice and the correct reason.
Each
correct answer was given a score of one. Chppendix -1)
The
Investigator administered
the
Diagnostic Test
in
Chemistry to a sample of 620 Educationally Backward students
studying in Standard IX. Out of 620, the scores of 370 students
were taken for item analysis.
Difficulty indices for the items
ranged from 0.09 to 0.7 showing a wide range of difficulty in the
items. Discriminating powers ranged from 0.32 to 0.65 and all of
~
them were considered acceptable according to ~ i e n(1971).
According to ~ i l b e r t ' (1977), work using multiple choice items
with four or five choices, student understanding of the conceptual
area was considered satisfactory if more than 75% of the students
correctly answered the item. The items for which more than 75%
of the students answered incorrectly were chosen as difficult items
and
the
corresponding
learning
points were
used for the
preparation of the Remedial Teaching Materials in Chemistry.
The details regarding the learning points (included in the
Remedial Teaching Materials in Chemistry) are given below:
--
---
~
,.
. ...
-
Methodology
-
~
4
I
N~rcleusthe centrul part
Electric charges of Electrons, Protons and Neutrons
Cot~tributionstowards the d i s c o v e r ~o f atomic ~ a r t i c l e s
F1-1
i'-JK~presettiaiion
1
o f a n aton,
111 I Oxidation And Reduction
of Oxidation
.
. . .. .. .....- ' o. f Reduction
3 Oxtdatlon based on Oxidation
- ..- . ~ y. .r .n.. .b..e.-r ...- .
. -I ' K ~ v l u ~ ~ ~b nr xov~d to t ~Oxrdnrior~Nurtlber
concept of Oxidation
concept of Reduction
--
1
-
11.
-
Methodology
-
KEME1)IAI. TEACHING MATERIALS IN CHEMISTRY
The lnvestigator prepared Remedial Teaching Materials for
the follow~ng topics in Chemistry for Educationally Backward
students studying in Standard IX
(i)
Periodic Table
(ii)
.4tontic Structure
(iii)
Oxidatior~& Reductior~
For the preparation of Remedial Teaching Materials, the
Investigator made a detailed analysis of the content and literature
related to the selected areas and identified learning points (LP)
Periotlic
Table
(LP=16),
Atomic
Structure
(LP=ll)
-
and
0.uidutiorr & Reduction (LP=9).
Each Learning point is explained with suitable learning
situat~ons, Charts, Pictures, Models. Experiments, Discussion.
Projects, Concrete situations, Problems
and Outdoor activities.
Provision for developing scientific skills and social skills were
given due importance while preparing the Remedial Teaching
Mater~als.
The
Remedial
Teaching
Materials
(prepared
by
the
Investigator) on the topics Periodic Table and Atomic Structure
are given below:
[Note: The Investigator prepared 3 Remedial Teaching Materials
on the topics, Periodic Table, Atomic Structure and Oxidation &
Reduction. But Remedial Teaching Materials on two topics viz.,
Periodic Table and Atomic Structure
108-3,441
, are given below.(pp
SCHOOL OF PEDAGOGICAL SCIENCES
MAHATMA GANDHI UNIVERSITY
KOTTAYAM
REMEDIAL TEACUING M A TERIALS
ON
PERIODIC TABLE
(STANDARD IX)
Prepared by
Supervised by
RAJESWARI. K
:
Dr. EXEMMAL. J
(Supervisirrg Teaclier)
Reader
Deparfmerrt of Educafiorr
Urriversity of Kerala
CFENE(DI,U
CH7N5;N3mRIAU
Remedial Teaching Materials on the topic PERIODIC
TABLE is subdivided Into 16 Units. Details are given in
pages 108-254. In each Unit, students are provided chances
Tor observation, classification, identification, discussion,
analysis and concept formation.
Suitable charts, models, examples, illustrations, life
situations are also used for developing new conceptslteaching
points. Practice session is given at the end of each unit to
test
tile level of attainment of the students.
Activities
and
Reference
Section
are
Extended
1.
given.
Achievement Test on Periodic Table is given at the end of
thc ~nater~al.
--
-~.
~~.
CONTENTS
UNIT 1
HISTORY OF CLASSIFICATION
OF ELEMENTS
UNIT 2
MENDELEEV'S PERIODIC TABLE
UNIT 3
MENDELEEV'S PERIODIC LAW
UNIT 4
MERITSANDDEMERITSOF
MENDELEEV'S PERIODIC TABLE
UNIT 5
MODERN PERIODIC TABLE
UNIT 6
THE MODERN PERIODIC LAW
UNIT 7
PERIODIC TABLE CHEMIST'S MAP
UNIT 8
GROUPS - VERTICAL COLUMNS
UNIT 9
PERIODS - HORIZONTAL ROWS
UNIT 10
THE ALKALI METALS
UNIT 11
HALOGENS
UNIT 12
TRANSITION ELEMENTS
UNIT 13
GROUP NUMBER AND VALENCE
-
ELECTRONS
UNIT 14
PERIOD NUMBER AND NUMBER OF
SHELLS
UNIT 15
ATOMIC SIZE DOWN A GROUP
UNIT 16
ATOMIC SIZE ACROSS A PERIOD
Methodology
INTRODUCTION
(l
\
1
i
fhe Periodic Table is a product of the
contr~butionsof chemists from many countries. It
has taken centuries of work to arrive at this
at rangement of elements.
I
(
Drnitri Mendeleev
1834- 1007) was a Russian chemist who drew up
c
He did this by clrarting
the t i ~ s tP e r ~ o d ~table.
tire known cl~emical elements
I
I
order of
irlcreasirrg atornic weight, altlrough we krrow that
l
it is tlre order of atomic number tltat is
I
!
\igrrijicant.
1
Tlrr
Modern
Periodic
Table
is
an
1I errcyclopedia of all the krrowrt elernerrts. It also
I
1
provirfes space to accommodate elemerzts yet to
be rlisrovered. Tlre periodic table is useful
1
because tlrere is regularity in tlre clzemical
1
properties of tlre elements.
I
\
/
'I'he arrangement of elements in the periodic
table is useful as it is possible to predict the
properties of an individual element from its
position. -l'he Modern Periodic table is a table of
all the chemical elements, in order of their atomic
numbers so that elements with similar properties
arc close to each other. The Modern Periodic
Table was desigtted by Hertry Moseley.
Merhodolow
]
~
1I
~
~
....~
SI. 1
No :
Learning ~oniII
Antome ~,avosie<-Dobereiner, Newland and Dmitri
1
/
-
I
lvanovich Mendeleev and Henry Moseley made several
(
1 attempts to classify elements
)
!
--
A
/-2
Mendeleev arrangd elements in the periodic table in the
I
1
I
Increasing
order of atomic masses
Mendeleev's periodic law states that physical and
chenl~calproperties of elements are periodic functions of
I
I
I
1
1
1
thelr atomlc we~ght
,
--
4
---
Mendeleev
I,.
first time in the history.
Mendeleev1 s periodic table does not precisely follow
I
i
1
-
I.
I
the order of atomic mass and some dissimilar elements
1
(
I
were arranged in the same group
.-
t
--
- - - -
5 , 7'he Modern penodic law states that the properties of
1
']'he Modem Periodic Table was designed by Henry
I/
Ihc eiements are arranged in the increasing order of
1
their atomic number
I
cle~ncntsare perlodic functions of their atomic number
/
,
0
~
.
~..~
I
11
11.
I
~
-
7
I
i
'
I
I
~
i ~ i . 7'here are 1 8 groups and 7 periods
~
.-
Periodic table
miy
be defined
varlous elements according to their properties, in a tabular
T--7
~~
The vertical columns in the Periodic Table are called
groups
1
II
There are 18 groups in the Modern Periodic Table
I
The horizontal rows in the Periodic Table are called
- . -
~
9
I
periods
I
tI
- .
I
II
There are 7 perlods
I
The Group 1 elements in the periodic table are called
+
10 I
I
alkall metals
1
The Group I elements are Sodium, Potassium,
11
,
I
Kubidlum, Caesium and Francium
I
-
.
. ..
.-.- -
The Group 17 elements in the periodic table are called
, I
/
I
halogens
I
11
(
The Group 17 elements are Fluorine, Chlorine,
Brom~ne,Iodine and Astatine
-
+
~.~~
he elements in groups 3-12 in the periodic table are
!
1
called trans~tionelements..
1 Period Number represents the number of shells in an atom
~~~
1 3
4
t
I
I
1
I
In Group I and 2, the number of valence electrons is
equal to group number
~i I'rorn the group 13 to 18, number of valence electrons
1I
I
I
I
I
; Atomic size increases from top to bottom in a group due (
, to Increase in number of shells
I
IS
equal to group number minus 10
-~
IS
/
I I Atomlc s u e decreises from left to right in a period due to /
---
16
1
Increase in the nuclear charge without increasing the
number of shells.
I
.. .
- --
I
I
-~~~~
~
~
--
~
.
~
~
~
--
~
Methodology
~
PREVIOUS
-.
. .~
I\
>>ha-.
I> ,
\
I,'
St~rrlentsrlre encouraged to recall the followitlg concepts:
Elements are pure substances made of the same
-I
kind of
atonls.
-I
Elements exist in solids, liquids and gaseous states
-1
Compounds are pure substances made of different
kind
of atoms
J
In an atom there are equal number of protons
and electrons
J
Atom~cnumber
IS
equal to the number of protons
in an
atom.
-1
Elcctl-ons in
shcll
an
atom
are
present
outside
the
and are arranged in shells
J
In an atom the outermost shell is called the valence shell
J
'l'hc eler:trons present in the outermost shell are called
valence electrons
,\'i
-
>
z h a s e I1
I
/
'
Stu(1o111.s
are erzcouraged to write the answers for the following
qlrestiotls
in
the space provided.(recalls different elements
prescJnt in the r~ature)
i
I
)
Two lighter elements
(i)
(ii)
( 2I
( 3)
Two elements in the
6)
gaseous states
(ii)
-1wo elements in the solid state
(i)
(ii)
(4I
'l'wo elements in the liquid state
(i)
(ii)
(5)
(0)
l'wo elements present in the
(0
atmospheric alr
(ii)
I he elements in water
6)
(ii)
( 7)
'fhe elements in Carbon dioxide
(i)
(ii)
~~
Methodology
~
(8)
T w o metallic elements
(i)
(ii)
(9)
'Two nonmetallic elements
(1)
(ii)
(
I O)
Two elements having isotopes
(i)
(ii)
(1 1)
Two elements used for making
(i)
ornaments
(ii)
( 12)
Two elements commonly used for (i)
making house hold utensils
(ii)
( 13)
Two elements used for making
(i)
weapons
(ii)
The most abundant element in
(i)
the atmospheric air
(ii)
( 14)
I5 I
The most abundant element in the (i)
earth's crust
(ii)
( 16)
An element used as thermometric (i)
liquid
(ii)
( 17 )
Thc elements present in
(i)
Common Salt
(ii)
Two coinage metals
(i)
(
( 18)
(ii)
I
NOW THINK
Make a list of other known elements (other than
questiorz rrumbers 1 to 16' pp
'Ir-9 to you
Box [ I ]
Nitrogen, Phosphorus, Sodium,
Potassium, Magnesium
I
Students are encouraged to identify that there are about 116
ele~r~ents
S~lrtlorrtsare errcourageci to fatniliarize the two illustratioizs
hclo~,
giljcvi
<:
- -.
~.~
~~
ILLUSTRATlON (I)
~--..-
Co11.\11iera
I ~ I U S ~shop.
C
Suppose Cds and tapes are placed in
gr.ozrps such as chart music, dance, melody, top hitz etc. This
nlcikr.\
it
easier. to,find the kind of music looking for:
Fig. 4.1 Arrangement of Cassettes
Lcr I
s~z~derit~
cot~pcire such a nlusic shop with an
~~i~c~ltr.s.sifierl
utie.
~
~
Methodology
~~
Lei t l l c ~stu[letzts consider the arrangenlent of books in a library:
111
c,ertain libraries books are placed in groups such as
nor~cis, shol-t stories, journals, dramas' scientific books,
hiogr-lr/~h
ies, rzuiobiographies, etc.
Iri
.SLIC./I
(1.5,
cerfair~other big libraries books are placed in groups
Arith~i~tic,
Botar~y, Chemistry, English Literature,
G'o~c,t.<rl
Kncl~~ledge,
Etzgineering, electronics, periodicals ,
ctc. ,2,f(rkesrile students aware of the advantage of such an
rrrt.rlt~gc~~~ctzt
cfbooks. Putting books into groups in this way is
calleti cltrssiji~itzg
Fig. 4.2 Arrangement of books in a library
~-
~
~p~
~
----
119
-
-
Methodology
-
Through the above illustrations students find out the
conkcnlence of classification and also encourages to think
about the advantage of classification in Chemistry.
'
Box [2]
Advantage of classification of elements
I
a
Made the study of elements easy
'
d
THINK AND
DISCUSS
F'rol~irlc oppor.turlity for. classiJLing the substances given in
BOX1.31. 1t1 rlifjer-ent wuys.
Box [3]
/'
I
/
'
\
Oxygen. water, Carbon dioxide, Hydrogen,
Sulphur,
Nitrogen,
Potassium
hydroxide,
ammonia, Aluminum, Nitric acid, Sodium
hydroxide, lodine, Zinc, Ferric Sulphate, Gold,
Carbon, Potassium, Ferric Sulphate.
\
I
-
Methodology
-. .
P~.o\,iri~ttg
opportuniv to classify the above list of substances
into tllc Jollowitzg c,utegories:
1
Solld, 11qu1dand gas
2 Elements and compounds
3
Metals and nonmetals
4 Aclds and bases
( 'lnssijj~i/lg
e1ement.s
-
-
Sulphur
Alitrniniurn
-
(Box 3) into solid, liquid and gas.
~
Water
Oxygen
Nitric Acid
Carbon Dioxide
~
~~~.
Nitrogen
I
St~rrlc,/lts( l i . ~ ' etirouraged to expand each group 191 adding
I'i.o\.ltli/lg oppor-tutzitj~ to recall the dgferent mode:,
c,lo.\ \c/ic.rrtiotl /nude bj, tliepupils:
S u b s t a n c e s c a n be classified i n different ways
of
-
--
-
-
-
Methodology
-
Students are ericouraged to record the action of Sodium,
Potassiutil, Iron and Copper with water (in the space
-
-
SI. 1~
!
~p~~
No.
~
,
. . . . .. .
..
...
Inference
Observation
Experiment
.
Vigorous
reaction
ACTIVE
METAL
Putting sodium in water
1
!
/ . .-
.
.
. . .
i
- -.
Putting potassium in
water
1
2
..
Vigorous
reaction
' I .
I
ACTIVE
METAL
,
I
1
.
I
-
-
I
3
.
1
Putting lron in water
/
INACTIVE
METAL
No change
.
!
I
4
Putting copper in water
No change
:
I
INACTIVE
METAL
r:-';.! rri
-- -
- - - .--.
-
Methodology
--
Encourrrgl~lg.studerlts to classlfy elements(Sodium, Potassium,
/rot1 (111dCopper) on the basis of their hardness.
~~
~
Experiment
Cutting sodium
metal with a knife
1
..
1
-
-~~
Cutting a piece of
can be cut
easily
SOFT METAL
j can be cut 1 som METAL
1
knife
.
+
col7per
C'utt~nga prece of
I Iron
Cannot be
cut easily
HARD METAL
identities the advantages of classification of elements:
/'
Classification of elements made the
study of elements easy and more
convenient
,,'
.
-
Methodology
.
-
I\
.
\\,/<
Y--'~
\
LET US
THINK AND
DISCUSS
1
HISTORY OF CLASSIFICATION OF ELEMENTS
UNIT 1
Learning Point
Antoine I,avosier, Dobereiner,
Newlands,
Dmitri
lvanovich
Mendeleev and Henry Moseley
made several attempts to classify
clemei~ts
~
~
~
~~
I
/
'
I'r.ovirlirig
oppot.tunity
to
acquire
irfol-mrrtion of
.sc~ic~rztrst.r
it1 thejieli ofclasslfiing elernerzts
/,'nr~lilicz/-isirrg
tlie i~?lportant
cltemists and their
c,or~trihutiorrsin clussijjing elenzerzts:
-
--
-
Methodology
-
The work done by Lavosier(1789)
-
-
-
-
Lavosier marked the beginning
of classification in 1789.
classified
the
then
He
known
elements into METALS and
NON METALS
1
Fig. 4.3 Larosier
1 CLASS I
IFICA
-
('I.AVOSIBK
--
TION
1
)c=>
--'
OF
1
CNTS
METALS
1
I
.
--
-
-
-
-
Methodology
Si111i('rlts(ire etlcout.ngeCf to go through the contributions of
Dobereitlev (181 7)
Dobereiner:
( I ) ldentified the triads (group
oftlzree sinzilar elements).
(i)
(
Litl~iurn,
.%ciium,
lJotnssiur~z
Fig. 4.4 Dobereiner
( 2 ) Used atomic mass as the basis
1
for grouping elements.
-
-
-- .
.-- -
1 ) o b c r c i n c r ~ Identification of Traids
I
-
-
-
Methodology
- --
Discussing the contributions of IVewlands (1 864)
0.
-
The English scientistNewlandsarranged the elements in
the order of their increasing
atomic mass. He argued that the
properties of eighth element was
repeated as the eight note in
musical notes (sa, ri, ga, ma, pa,
dha, ni, sa). Based on this
observation
Newland
~ i g4.5
. Newlands
postu,lated
the
Law
of
Octaves(simi1~zribetween e v e y eighth element like the
eig/rt/~note oj'nn octave in rnu:;ic). Newlands
was
the first to use numbers in a serial order
and to predict periodicity.
Newla~~dsc
2
d L,aw of Octaves
DESCRIBING THE MAJOR CONTRIBUTIONS OF
Fig. 4.6 Mendeleev
I'ROC'ELIURE
ADOPTED
BY
MENDELEEV
CLASSIFY 1NG ELEMENTS
More than 60 elements known at the time was
ii
He wrote the atomic mass and properties of
elements on separate cards.
a
a
a
He made a comparative study,
Published :I table,
And Classified the known elements.
FOR
--
-
--
Methodology
--
-
-
Classification of elements by Mendt:leev
Mendeleev's periodic table
, , ,
, ,
PBBIODIC BYSTEM OF TEE ELEUESTS IN GROUP0 AXD EEBI&&
j
/
-...
1
0
!
nz,
- - H i
1
I
-
--
ORDUPE
11
I
..-
..
or L L t Y E r n
-.
........
! v n ....VII
....................
.-.
i
1x7
,
-i
'1
-
-.
'
VIIX
,
I
-,
-
.....
Rat& W
C,
Dnoa
'8x0
1
118
181.9
1"
137-4
U.
.Ih~oool rlum
j
! 18U
, -
i ~ aoe
140
PT-I
*
I
I'cl.~odlc '1 able
NL..
-
l s l . . . ., l
-
-
:
t
.
I
i
-
---
Metkodolom
Sti~derrtsare encouraged to develop concept about Mendeleev's
Periodic Table(throug11observation, discussion and questioning)
( I ) What is the basis of classification
of Mendeleev's
periodic table?
(2) Whether the elements are arranged in the ascending or
descending order of mass numbers?
(3) How many rows are there in the table?
(4) How many columns are there in the table?
(5) How many elements are included in the table?
i
C'ONCEPTS OF MENDELEE V
(1) Numbered the elements according to
lie atomic mass(mass number)
(2) Arranged in the ascending order
(increasing order) of atomic mass
(3) There are Six rows
(4) There are Eight columns
(5) Sixty elements are included in the
\
table
\\-.
--
-
DISCUSSING
I
THE CONTRIBUTIONS OF HENRY
Methodology
MOSELEY
-
Fig. 4.7 Henry Moseley
Henry Moseley, an English scientist proved
that it is the number of protons, ie. the atomic
number, that can be called the identity card of
an element.
Moseley designed the Modern
Periodic 'Fable.
-
Methodology
- -. - ---
llobereiner was the first to identify the
triads
Iloberneiner was the first to use the atomic
mass as the basis for grouping.
Law
of
octaves
.was formulated
by
Newlands
Mendeleev first listed the known elements
in an ascending order of their atomic mass
Moseley developed the Modern Periodic
'I'able
,.---
,
,,
_-
Scientific Terms / Concepts
/'
LAW OF OCTAVES
TRIADS
x.,
.
.
.~~.~.
i
)
--
QG
Methodology
- --
-
CONCLUSION
Lavosier, Dobereiner, Newlands,
Mendeleev and Henry Moseley made
several attempts to classify elements
.-
,-T-------
EVALUATION
blanks. Choose the correct answer from
tile hriickcts
Fill
irl rile
(I )
Law of octaves was formulated by --------(Mendeleev, Newlands, Dobereiner)
1
[ ( 2 ) The triads were first identified by -------(Mendeleev, Newlands, Ilobereiner)
1 ( 3 ) -------lirst listed the known elements in the order
of their atomic mass
(Mendeleev, Newlands, Ilobereiner)
Ii ( 4 )
I
Modern Periodic 'Table was developed by
(Mendeleev, Moseley, Dobereiner)
-----
I
1 ( 5 ) What is the basis of classification of
I
Mendeleev's Periodic Table?
( 6 ) Give an example for a Triad?
-
- --
UNIT 2
-
--
-
-
.
.
-
--
Methodology
MENDELEYEVX PERIODIC TABLE
earnin in^ Point
Mendeleev arranged elements
in the periodic table in the
increasing order of atomic
masses.
I'uplls have learnt that different elements show different
propert~es. The) have also learnt that Elements are
classified on the basis of atomic masses
DEVELOPING 'TI-IE CONCEPT OF PERlODIC TABLE
1:ncourage pupils to go through the Mendeleev's Periodic
Table (PT-I ) and provide opportunity to find out what is a
period and what is a group..
Methodolow
Let tlrc~studet~tsgo tllrough the Mendeleev's Periodic Table:
(PT
I)
Ei~c,orii.clgr the students
to
arzsMier the following questions
oh.\ rt.Isltlgt l ~ Mendeleev
r
's Periodic Table.
I . How many columns are there in the table?
------------------
2. Hoe many rows are there in the table?
------------------
3. What is the basis of classification?
------------------
I<~icourages
to ldent~fyGroup and Period
I'ro\idc opportunity to locate and find out the periods and
groups
I
1-
I
,>
I;.
Periods are Horizontal Rows
I--~
j
-
1
G
G r o u p s are Vertical C o l u m n s
--Methodology
Mmdeleev's Periodic Table elements
111 r l ~ c
ar-c arranged in t h e increasing order of atomic
masses
I'lle horizontal rows in the periodic table are
c;~llcclgroups
-
'l'he vertical columns in the periodic table are
callcd periods
__--
-
--
/
,
-
i
\
Scientific Terms / Concepts
RIENDELEEV'S PERIODIC 'TABLE
..
--
----
1
Mendeleev arranged elements in the
periodic table in the increasing order of
atomic masses
-
-
EVALUATION
(
..lri.s\z~rrrhc ji,llo~vitzg questions:
;
i.
f i l l in the blanks:
a.
l~iorizontalrows in the periodic table ar
called ---------
!
b. Vertical columns in the periodic tab1
!
I
I
are called ------2
LL hat
IS
the basis of classification of
blendeleev's Per-lod~ctable?
.-
-
I
_I
-
-
UNIT 3
-
-
. --
-
Methodology
--
MENDELEYEV'S PERIODIC LAW
-
Nlendeleev's periodic law
states that the properties of
l'~inctions of
t h e ~ r atomic
masses
I
.~
-
~
p~
-
PREVIOUS KNOWLEDGE
~~~
~
~
1.c.r
~
~
illt,
>
>..
. -.-
7
,
'
~~l~ilrirew
discuss tlze special features of Mendeleev's
Periodic Table
L>~.\c,rrc.>~ng
ille c~lzaracter.isticsof Mendeleev 's periodic table:
Stlrtlcvlt\
1111rll 1110
czt.c.
encouraged fo answer the following questions
help of Mendeleev's Periodic Table (PT - I)
.
~
~
Methodology
I . I lo\\ many elements are their in the table?
...................
2. I lo\\ niany groups are there in the table?
...................
3. I lo\\ niany pcr~odsare there in the table?
...................
4. Whar 1s the basis of classification?
...................
5 . What 1s the order of arrangement of elements'? ...................
0 . As you proceed from left to right in a period,
\vliar changes do you notice in the atomic mass
ol'ele~iients'!
...................
7. li'licn Mendeleev arranged the elements in
the order ol' increasing atomic mass, did the
c l e ~ ~ l c ~\vitIi
l t s similar properties fall on
;I
sroup or i n a period'?
...................
I'~.o\.rdt.opportunity to recall the seasons of India and
tlreir oc~c.za-rc~trce
itz a periodic ??.tanner(understanding
tlre ir~err~~~rrg
of per-iodicityl
Stlrrier~~s
icic.r~t@i'tlze periodic roperti ties of elements by
oh.sc~~.~~trtiorr
ulld disc~rssion.
-
--
Methodology
--.
Provrtl~tlgopportunities to arrive at the Mendeleev's Periodic
Law (through discussion and observation of Periodic Table)
Mendeleev's Periodic Law
THE PROPERTIES OF ELEMENTS ARE
PERIODIC FUNCTIONS OF THEIR ATOMIC
MASSES
--
--
--
-
--
-
In the Mendeleev's Periodic Table, the
properties of elements are arranged the
properties
of
elements
are
functions of their atomic masses.
periodic
1
1
I
I
The
i
Mendeleev's
periodic
law
states that the Properties of elements are
periodic functions of their atomic masses
--:
EVALUATION
,-?
i
i
1
I
.~II.\
I
( 1)
i
:
uret-f/refo//olr,rtlg questions:
State Mendeleev's periodic law
( 2 1 What is the significance of Mendeleev's
periodic table in the classification?
I
I
( 3 ) l l o u many periods are there in the
klendeleev's periodrc table'?
i
j
( 4 Ilou many group!; are there in the
i
Mendeleev's periodic table?
I
i
( 5 ) What
are
the
characteristics
hlendeleeu's per~odictable?
-
--
--
--
of
I
_I
I
I
I
-
UNIT 4
--
.
-
Methodology
MERITS AND DEMERITS OF MENDELEEV'S
PERIODIC TABLE
.---
-
---
Learning Points
(i) blendeleev
exhaustively
classilied the elements for the
first tlme in the history.
( i i ) Mendeleev' s periodic table
does not precisely follow the
o~-dcro l atomic mass.
(III )
home
dissimilar
elements
\<ere arranged in the same
groLll1.
~-
~
PREVIOUS \<NOWLEDGE
~
\tutlcnt\ ha\e learnt about Mendeleev's Periodic Table and
I'criodic 1,aw ( U n ~ t s1 to 3)
Methodology
Di.sc,~r.\.\
I ng the clzuructeristic feutures of the Merzdeleev's
Periodic Table (,Ttuderzts (we encouraged to find the answer
, f i illc
~ follovr,uzg qirestiorls based on tables :pp ........)
Is the increasing order of atomic masses of elements strictly
(1)
adhered to':'
(2) Are elements with different properties included in the same group?
( 3 ) Wilat 1s the action of Potassium with water?
(4) \+'hat 1s the action of Copper wit.h water?
( 5 ) U'liat about the hardness of Potassium and Copper'!
(0) ('an I'otassluni and Copper be included in the same group?
ANS\\'I.:K KEY
-
J
(
0
-
-
- --
1 ) I)oes not precisely follovv the order of atomic
Inass
( 2 ) Elenlents with different properties are
included in the same group (eg:- Potassium
21nd Copper)
1
1
(3)
I'otnssium reacts vigorously with water
(4)
(:opper is passive towards water
( 5 I'otassium is soft while Copper is hard
(0)I'otassium and Copper cannot be included in
the same group
I
I
I
1
-
-
-
-
. .
144
Methodology
- .. . .
Students are encouraged to develop concepts about the me& and deme~?Sof
Meodeleek 5 Per/od/c Table (through observation, discussion and questioning)
Ident~iylngthe major merits and dei'ects of Mendeleev's Periodic
Table
r~
1
I
~
--
MERITS
-
-
-
T
t
I<xhaust~veiyclassified the Does not precisely follow the
clenients lor the first time
-
! order of atomic mass
i
1
I
I
T o m i dissimilar elements are
arranged in the same group
-
-
--
Mcndelecv arranged t h e non elements in a
t a b ~ ~ l form
ar
* M e i ~ d e l e e v exhaustively
classified
the
clcments for the first time in the history.
I
Mcndclcev's
periodic
table
does
not
precisely follow the order of atomic mass.
Some dissimilar elements were arranged in
/I
the same group (e.g., K, Cu )
- -- -
145
. -
-
-
Methodology
--
Mendeleev exhaustively classified
the elements for the first time in the
history.
(2) Mendeleev's periodic table does not
precisely follow then order of
atomic mass.
(3) Some dissimilar elements were
arranged in the same group.
(1 )
i?
EVALUATION
1 A r i s ~ i vihefullowing
~.
questions
I
I
I
1
( I ) Write the merits of' Mendeleev's periodic
table
I
1
1
(2) What
are
Mendeleev's
the
major
demerits
periodic table?
of
-. - -
-
-
-
-
--
Methodology
MODERN PERIODIC TABLE
UNIT 5
-
- -
Learning points
(i)
'l'he Modem Periodic Table
was designed by
Henry
Moseley.
( i i ) I'he elements are arranged
i n the increasing order of'
their atornic number.
l here are 1 8 groups and 7
(11 I )
per~ods In
the
Modeni
I'er~od~c
I'able
--
.-
J,
---
PREVIOUS KNOWLEDGE
-
>
---I/
I'rovitiitlg opportutlity to recall the concept of Period
~ t r t Group.
i
-1
1 lor~zontalrows are called periods.
J
Vertical columns are called groups.
~
-
~~~
~~~
Methodology
~~
1x1 /he studetlt.~discuss the special features of the Modern
Pel-iotlic fablr
Disc~~r.s.slngthe characteristic properties
of the Modern
Perlotllc Table (wit11the help of Periodic Table).
Modern Periodic Table
i.\
-
-
- . --
Methodology
Stuticv~tsrrre rrlcouraged to write the answers for the questions
give11helow. (Observing PT-2)
I i llow many groups are there in the table?
................
( 2 ) How many periods are there in the table?
................
(3 ) Name the smallest period.
................
( 4 ) Name the members of the first period.
................
(
( 5 ) ( i ~ v ethe atomic numbers of the first
per~odelements.
( 0 ) Name the members of the second period.
( 7 ) Whether the elements are arranged in the
Increasing or decreasing order of the
atomic
number?
................
................
Methodology
-
Dcvelopl~lgcliagrat?zmatic representation of 8 MAZNgroups (I,
2, 13, 14, 15, 16, 17and 18).
B
13
A1
31
Ga
49
In
81
TI
ldcntifying
C
14
Si
32
Ge
50
Sn
82
Pb
N O F N e
15 16 17 18
P S CI Ar
33 34 35 36
As Se Br Kr
51 52 53 54
Sb Te I Xe
83 84 85 86
Bi Po At Rn
*
Lanthanides (14 elements)
**
Actinides
7
periods
(Observing PT -- 2)
in
(14 elements)
the
Modern
Periodic
Table
-
~
..
-~
Methodology
Providing opportunity for the pupils to locate groups 3 to 12
*
[,anthanides (14 elements)
**
:\ctinides (14 elements)
Elzcoilt-age the students to develop the concept about the
u~.r-cltrgernzerzt of elements in the Periodic Table- CI
( / I Z I . O ~ ~ oh~ervution
~/I
and discussion)
Elements are arranged in the increasing order of
atomic numbers.
--
-
-
--
Methodology
Stutlrrlts are erzcouraged to answer the following questions
(hn.sc~tior1 the Modern Periodic Table.)
What is the basis of classification?
How many horizontal rows are there?
How many vertical columns are there?
Where is the place of transition elements?
How many rows are there below the main block?
Name the incomplete period?
Name the shortest period:?
How many elements are there in the shortest period?
How many elements are there in the second period?
tlow many elements are there in the third period?
Ilow many elements are there in the fourth period?
How many elements are there in the fifth period?
How many elements are there in the sixth period?
Name the elements in the first period ?
Name the first element in the second group?
Name the first element in the fifteenth group?
Name the first element in the seventeenth group?
How many members are there in the eighteenth group?
Name the first element in the last period?
Methodology
ANSWER KEY
I1
I
~
2
-
-
,7 horizontal rows
1 18 vertical columns
3
~
4
-
~
Increasing order of atomic
number
4
-
0
1
~
~
-
p~
~
~
~
p
~
-
~
~
Between groups 2 and 1
~~
~
--
I't.o~~itlit~g
o y ~ p o r t u n ito~ ~I d e n t l . the Number of' Groups and
P~riorlsin Tlze Modern Periodic Table
\
PERIODS = 7
\-/
Encour-clging studer~tsto recall the name of the scientist who
developed the Modern Periodic Table
--
Henry Moseley (Figure 4.7), an English scientist
proved that it is the number of protons, i.e., the atomic
number, that can be called the identity card of
an element.
-- -
In the Modern Periodic Table, there are
18 groups
There are 7 periods in the Modern
Periodic Table
Henry Moseley designed the Modern
Periodic Table
Elements are arranged in the increasing
order of atomic number in the Modern
Periodic Table
-
Methodology
-
CONCLUSION
(1) The Modern Periodic Table was
designed by Henry Moseley
(2) The elements are arranged in the
increasing order of their atomic
number in the modern Periodic
Table
(3) There are 18 groups and 7 periods.
I
EVALUATION
( A~isivcrthefollowirzg questions:
I . How many periods are there in the
Modem Periodic Table?
2. How many groups are there in the
Modem Periodic Table?
1
3. Who designed the Modem Periodic
18blez?
4. What is the basis of classification of
Modem Periodic Table?
i
I
I
-~
~
-
..
~
THE MODERN PERIODIC LAW
UNIT 6
-
-
Methodology
--
Learning Point
'l'he Modern periodic law
states that the properties of
I1
lilnctions of' their atomic
I
number.
I
-
~~
PREVIOUS KNOWLEDGE
.
~~
Students have learnt about MENIIELEEV'S PERIODIC
I At3l.t: (llnit 2 and 3)
/'i.o~,itio~g
o/~poi.tzuzit~~
to I-ecalltlze following concepts
C ~ ~ O L I Pare
S vertical columns in the periodic table
J
Per~odsare horizontal rows in the periodic table
-
-
- --
-
Methodology
Sttctle/lt.c (Ire etlcouraged to develop the following concepts
tllr.o~c,ylrohservc~tion,discussion and questioning: (Providing
oppo/.iu/~lty
t o observe the Modern Periodic Table - PT - 2 )
(G'i\:utg czrzswer-s to thefollowing questions)
( 1 ) How many groups a r e there in the Modern
Periodic table?
(2) How many periods a r e there in the Modern
periodic table?
(3) Which is the incomplete period?
(4) Which is the shortest period?
(1)There are 18 groups in the periodic table
(2) There are 8 periods in the Periodic table
I
I'
I
(3) The eighth period is an incomplete period
'(4)
First period is the shortest period
,--
I
tile Oasis~ of clrrssifkation
I
of Modern Periodic Table
tl~~.ot{gh
obs~rv~~tzon,
discussion and based on the structural
~.c/~/.e\rllfatrolz
qf the Modern Periodic Table (PT-2 & PT-3).
~
I
-.
--
. -
Methodology
-
Methodology
. --
-
Provldirlg opportunities to go through the periodic tables:
(I'T
-2 & 3), Identifiing
the symbol and rztomic numbers
---.
The first element in the periodic table and its
atomic number?
I
--
-
I
The second element in the periodic table and its
atomic number?
/HELIUM]
I
I
.
~
1Le third element in the p
e
r
i
o
d
i
c
~
'I'he tburth element in the periodic table and its atomic
I
atomic number?
(
number?
1 BERYLLIUM 1
l
.
.
Methodology
.-
Namc the third element and what is its atomic number?
Sflrdctr~.\(Ire errcouraged to find out the number of periods in the
Periortrc. 7crhle
1
- - -~
7 PERIODS
1
Reason
4HORIZ","J
.
I
Stictlc~rirs rrrr ericouraged to find out the number of groups in
tlir I'ct-rodic Table.
..,
1
~
-
I 8 GROUPS
1-4
] Reason
~
COLUMNS
Errc.orrt.c~g~~
.~tzrclet~ts
to ident~jj the order of arrarzgement of
c~Ic~~rrorr~.\
rrr t l t ~Ptv.iotiic 'lilbie(increasingorder of atomic number).
Lct the students represent the elements in:
I'ERIOI)
Atomic
Number-
.
.
-
---I
---
Methodology
--
-
-
@ @ @@@@
Number
7
elements
.
--
-.
ph a- s e I ? 9
1,
t
Nuniber
i
--
--
a8
@ @
/--
-'
KEY POINT
,/
,
'
\
\
=+
The elements in the
Modern Periodic Table
are arranged in the
increasing order of
atomic numbers
\-.\-/
0a
-
--
--
-
.
Methodology
.
Provrtle opporrunity to compare the Modern Periodic table
wit11Mendeleev's Periodic Table:
Students are encouraged to answer the following questions:
I.
IS THE BASIS OF C1,ASSIFICATION OF
WIIAI'
ELEMENTS
IN
THE
MENDELEEV'S
PERIODIC
TABLE'?
2.
WHA'I' IS THE BASIS OF CLASSIFICATION OF
I:I,EMENI'S IN THE MODERN PERIODIC TABLE?
Stutic~~~ts
identijj the periodic properties of elements by
ohsc~i.l,t~tion
and discussion.
-
A~.~-ii<ing
at the Modern Periodic Law by observation and
tlisc,ll.s.sion.
'
,
i
r
/
\
'\
Modern Periodic Law
states that the properties
of elements are periodic
functions of their
\.
atomic number
1
k
u
--
.-
Methodology
-
-
'me elements are arranged in the increasing
order of their atomic number
There are 18 groups in the modern periodic
table
There are 7 periods in the modem periodic
table
/--
Scientific Terms / Concepts
MODERN PERIODIC LAW
'..
..
\-.--
@
?CONCLUSION
1 1
/ I
Modem Periodic Law states that the
are
functions of their atomic number
properties
of
elements
periodic
I
I
-.
-
--
j
-
i
I
1
Methodology
--
EVALUATION
Answer the following question:
(1) flow many periods are there in the modem
periodic table?
(2) How many groups are there in the modem
periodic table?
I
(3) Who designed the modem periodic table?
(4) What is the basis of classification in the
modem periodic table?
UNIT 7 PERIODIC TABLE - CHEMIST'S MAP
-
--
--
Learning Point
I'eriod~c table may be defined as
the
arrangement
elements
of
according
various
to
their
piopert~es,in a tabular form
~
~
I:>
~
PREVIOUS [<NOWLEDGE
~
f'rov~diwgopportunity to recall the following facts:
J
Mendeleev arranged elements in a table.
I'lie horizontal rows in the periodic table are called
periods.
a The vertical columns in the periodic table are called
groups.
u
In Mendeleev's Periodic Table, elements are arranged
in the increasing order of atomic mass.
u
In Modem Per~odicTable, elements are arranged in the
~ncreasingorder of atomic number.
-
-
--
-
-
Methodology
Stutlents ure encouraged to recall the concepts (C2and C3).
Classifcation of elements in to groups
made the study of elements easy.
I'
Arrangement of elements irt rows and
columns are based on the properties of
elemettts.
E11c.olrrclget l ~ estudents to answer the following questions with
the hrlp qf'Mendeleev's Periodic Table(PT-I),.
I.
I low many groups are there?
2.
Iiow many periods are there?
3.
\Vhat is the basis of classification?
4.
As
you proceed from left to right
in a period, what changes do you
~ioticein the atomic mass of elements?
- ..
-
-
-
-
Methodology
Modern Periodic Table
St~rdetrtsare ericouraged to answer the following questions with
the lielp of Modern Periodic Table,.
I.
How many groups are there?
2.
blow many periods are there?
3.
What is the basis of classification?
4.
As you proceed from left to right
i n a period, what changes do you
notice in the atomic mass of elements?
-
Methodology
~
Discirssitlg
tlw position
Mrrgne.slw?l,
of Sodium, Potassium, Iron,
Oxygen, Nitrogen, Gold, Silver, Aluminium,
Clilorine and C,'opper itz the periodic table
1
1
I
I
In the Periodic table, the elements are
arranged according to their properties
~t
CONCLUSION
Periodic table is the arrangement
1
of various elements according to their
properties in a tabular form
EVALUATION
---
-
Arlswer thefollowing questions:
I
/
1. What do you mean by periodic table?
2. What is the use of periodic table?
I
I
-
Methodology
-
-
UNIT 8 GROUPS VERTICAL COLUMNS
--
--
-
-
-
Learning Points
The vertical columns in the
(I)
periodic table are called
I
( ~ i )There are 18 groups in the
Modern periodic table
I
PREVIOUS KNO
--
.-
L)iscussing tlze clzuructeristics of MODERN PERIODIC
72 BLf:'.
(fJro~:icling
opportunity to recall that there are vertical
columrts in tlie periodic table)
Studerzt.s ure eizcouraged to go through the Modern
periodic table (PT-2) and to find out the number of groups
irr IIILJ periodic table
-
Methodology
-.
Irientqying the name of each group
-.
----
GROUP
--
NAME OF THE GROUP
1
Alkali metal
..-
Alkaline earth metal
2
Transition elements
.-
--
Nitrogen Family
15
- - -
16
-
-
17
Halogens
18
--
~
~
/
1 Noble gases
-
I
'
Develops the fact that Groups are
/
/-"
Scientific Terms / Concepts
//
k*
GROUP
'
1
\------
I
..-
-
Methodology
-
-.
-
Attention
Vertical columns in the periodic table are
called GROUPS
There are 18 groups in the Modern
periodic table
Groups are also termed as FAMILIES
Q
CONCLUSION
(1) The vertical columns in the periodic
table are called groups
(2) There are 18 groups in the modern
Periodic Table
'LA'
a-
7
EVALUATION
/ Ar,swer thefollowing queslions
I
:
I . Define group
2. How many groups are there in the Modem
Periodic table?
3. Name the following groups:
I
a. Group 1
I
UNIT 9
--
--
-
PERIODS HORIZONTAL R O W S
---
/'
Learning Points
( i ) The horizontal rows in
the periodic table are
called periods
I
( i i ) There are 7 such periods
I
---Y
PREVIOUS
- -KNOWLEDGE
J
Recalling the characteristics of MODERN PERIODIC
rABL E (PT - 2 )( Refer Unit 5 )
u
Providing opportunity to recall that there are 7 horizontal
rows in the Periodic table
Stur1er~t.s Lire erzcouruged to go through the MODERN
PEHIOLl/C' T,iBf,E and to find out the rtuntber of PERIODS in
rlle 1'er.rodrc k b l e (PT-2)
--
-
-
.
Methodology
.
Encovrrrge studerzts to prepare a table representing the
rzurrihel- of elerrtents in each period with the help of Modern
Pel-iotiicx Table (PT-2)
-
~~
Period
No. of elements
1
2
-.
~
8
2
~~
~
.--. .
~
~
~
-
-
~
-
p
~
8
3
-..
..~
18
4
---
~
~
~
5
.
6
--
~
7
.- -
INCOMPLETE
~~
L)evclo/~itzgthe concept
(C4)about the number of periods in the
/--
There are seven periods in the
Modern Periodic Table
-.-
-
-
Methodology
----
1 DO YOU REMEMBER I
r
How many periods are there in the modern periodic
table?
r Name the shortest period?
>
How many members are there in the shortest period?
>
t~lowmany members are there in the second period?
>
Name the incomplete period
r
Which is the longest period?
r
How is Group 6 and Group 7 differ from other
periods‘?
r
Name the first element in the third group?
i Name the last element
T
in the fourth group?
Name the group to which the first member of each
period belongs to
r
Name the group to which the last member of each
group belongs to?
-~
~
Methodology
~
Lanthanides and Actinides
Stutlei~tsure provlded opportunity to find out tlze position of
laritltariides and actinides in the periodic table
Developing the layout of Modem Periodic Table and helps to
identify the position of Lanthanides and Actinides
LAN rHANlDES
ACTINIDES
1 1 1 1 1 1 1 1 1 1 I I
Fig. 4.8 Lay out of Modern Periodic Table
Loctrrlng t l ~ rposition o f Lanthanides and Actinides in the
Perrodrc Table( wit11 the help of PT-2 & Figure-23)
,,
\
Lanthanides
PERIOD 15
Actinides
PERIOD 7
-..
-
-
Methodology
-
Developing t l ~ econcept (C5)about Lanthanides and Actinides
\
\-
Lantltanides and Actinides are placed
as separate rows under the periodic
table
The horizontal rows in the Periodic table
are called Period
There are 7 periods in the Modern Periodic
table
Lanthanides belong to sixth period
Actinides belong to seventh period
Lanthanides and Actinides are placed at
the bottom of the main block in the periodic
table
//
_
,
'
/
Scientific Terms / Concepts
/'
PERIOD
\
,
L.1'
LANTHANIDES
ACTINIDES
1
-
.-
-
-
-
Methodology
--
7-
(1) The horizontal rows in the Periodic
table are called Period
(2) There are 7 periods in the Modem
Periodic Table
1
!
I
Answer the following
questions
I
1I
1
( 1 ) Define a period?
I
1
(2) How many periods are the in the
Modem Periodic Table?
( 3 ) Say
whether
the
Lanthanides
and
Actinides constitute discrete periods?
1
Methodology
-
.-
UNIT 10 THE ALKALI METALS
Learning Points
The Group I elements in the periodic
(I)
table are called alkali metals
( i ~ They
)
are
Sodium,
Potassium,
Rubidium, Caesium and Francium
and are active metals
DISC LlSSlNG Tt1E CHARACTERS OF A GROUP
I'rovltie opportunity to go through thefirst group in the
Modern Periodic Table
.~
3
1
1,i
Lithium
,
II
Na
1 Sodium
~
,
19
I
ti
!
Potassiu~n
jl-I<b
:/ Kubedium
I
1
5s
('s
Caesium
.~
87
Fr
Francium
+GROUP I :
THE ALKALI METALS
--
---.
-
Methodology
Studeizts uve asked to make display cards
slzowirzg the atomic number and symbols
of
alkali metals.
Students carrying the
display cards showing the atomic number
and symbols of Alkali Metals are asked to
.face the whole class. Students in the class
write down the members of Alkali Metal.
Provlditlg opportunity to compare properties of elements of
First Group.
Encouraging students to conduct the following experiments.
-
Nu
/
Experiment
Observation Inference
--
Can be cut
easily
Soft
b Cutting Potassium with Can be cut
easily
a knife
Soft
a Cutting Sodium with a
knife
1
...
~
-
Vigorous
reaction
Reactive
Vigorous
reaction
Reactive
Burns
vigorously
Reactive
Burns
vigorously
..~.
Produces
a Reacting Sodium with
I
White
C: hlorine gas
i
powder
...
1-bkeacting ~ o t a k i u mwith Produces
White
Chlorine gas
powder
Reactive
a Treating Sodium with
ater
1
b P ~ r e a t i n gPotassium with
water
..
t a - i u r n i n g Lithium in air
3
-.
.
~
I-bBurning Sodium in air
1
~
React
violently
React
violently
Developng the co/zcepts C6and C7about Alkali metals (with
tlie //rip of' experinlent, observation and inference)
Proviile opportunity to recall the formulae of some compounds of
Soctiir~i~
and Potassium and identify the similarities between the
for~nuluo f the cori~poundsof Sodium and Potassium
Compound
s of sodium
SI.
No
Formula
Compounds
of potassium
Formula
I
Chloride
2
/ Sodium
Chloride
Na20
I Oxide
Potassium
Oxide
I
sodium
Carbonate
3
I
1
N ~ ~ C Potassium
O ~
Carbonate
Kz0
1
K~CO~
--
Sodium
Nitrate
NaN03
Potassium
Nitrate
KNo3
-
-
--
-
-- .
Methodology
Striderrts are provided with pieces of Sodium, Potassium,
Soriirrrn Choride, Potassium Chloride, Sodium Sulphate
and Lithiurn Chloride. They are asked to place the above
s~rbstartcesorte by one in a Bunsen's Flame.
OBSERVATION
(3
/-
i
Y'
---,
Alkali Metals and their
cornpounds give bright colours
when placed in a Bunsen's Flame
-
L)et,elop~rzg
thc7
Concept (Cs) about the similarities in
properties oj'Alkuli tnetals
C8,) Alkali Metals show sintilor properties
, -\-.~
--
-
-
Methodology
-
Provldr opportunity to identlh the mode of storing Sodium
and Potassium
POTASSIUM
Sodium and
Potassium
,
METALS AND
ARESTORED
UNDER OIL
handled with
\
'
.\
U
ldeni!fies tlze reactivity of Sodium and Potassium
Encolrruge students tofind out the reason for the Group I
elerrrerrts slrowirzg similar properties
Recc~llitlgthe concept of valence electrons and their role in a
Provide opportunity tofind out the electronic conjiguration of
alkali metals.
Element
Lithium
Li
Sodium
Na
Potassium
K
Rubidium
Rb
Caesium
C: s
Franciurr~
Fr
+d=Identifvlwg
.,
the nunzber ofvalance electrons
-
n
u
All Group 1 elements have one valence electron and
that is why they show similar properties
Developing the Concept (C9)about the nature of valance
electrons in elements in the same group
Atoms of elements in the same group of
tlie periodic table have the same number
of valence electrons
-
--
. .-
Alkali Metals are Lithium, Sodium,
Potassium, Kubedium, Caesium
and
Francium.
They are soft and reactive metals
They have only one valence electron.
They all show similar properties.
/
/
Sctentific Terms / Concepts
ALKALI METALS
LITHIUM
I
1
SODIUM
I
\
POTASSIUM
RUBEDIUM
CAESIUM
\
\
,
',
FRANCIUM
'\--
Methodology
-
-
-
(1) The Group I elements in the periodic
table are called alkali metals.
(2) Alkali metals are Sodium, Potassium,
Rubidium, Caesium and Francium
and are active metals
1
EVALUATION
1
Fill in the blanks:
( I ) First Group elements ~nthe Periodic
Table are called ----(2) Alkali Metals contain ---- valence
electrons.
(3) First element among the Alkali
Metals is
11 Answer the following:
( I ) Name the Alkali Metals.
(2) Alkali Metals show similar
properties. Why?
(3) Sodium and Potassium are kept
under Kerosine. Why?
--
-.
-
UNIT 1 1
-- - - -
~
-
-
Methodology
HALOGENS
~p~~
/"-
F
Learning Points
(i)
'I'he Group 17 elements in the
periodic
table
are
called
halogens
( i i ) They are Fluorine, Chlorine,
Bromine, Iodine and Astatine
and are reactive non-metals.
\
~-~~
PREVIOUS
/'r.ol:ide 0/7portunitj)to recall
J
J
l.luor~ne,Chlorine, Bromine and Iodine are non-metals.
I'hey are d~atom~c
molecules
11iscus.sing the Characters of a
Group
--
-
-
.
Methodology
--
Provide opportunity to go through the seventeenth group in
the Modern Periodic Table
GKOUP 17
+
HALOGENS
ACTIVITY I
Fluorine
Students are asked to make display cards
showing the symbol and atomic number of
halogens (F, C1, Br, 1 and At).
Bromine
1 '
lodine
-
- -
I
Students
carrying the display cards showing the
symbols and atomic numbers of halogens
are asked to face the whole class.
1 students
All
in the class write down the
1 members of halogens.
Corrrl)irr.irzg the properties of elements of Seventeenth group
--
---
--
Methodology
-
E~lcoltr-c~gesto identlfi the physical state of existence of
Diagramatic
representation of
halogen atom
tlalegons
...........
State of
existence
...
Bromine
LIQUID
Br2
~-
.................
Iodine
12
a
(30CO
CE (3000
SOLID
Iderrtifjtirrg tlte common properties of halogens (Questioning and
discrrssiorr and references)
I . Iiow many atoms are present in
one molecule of Fluorine'?
......................
2. ('hlorine 1s a diatomic molecule. Why? ......................
3. Name the l~quidHalogen
4. What 1s the state of existence of
t l u o r ~ n eand Chlor~ne?
......................
--
-
--
-- -
Methodology
-.
Idenfqying the similarities between the formula of the
conzpounds of Fluorine and Chlorine
- --potassium
-- -
- -- -
Sod~umChlonde
Sodium Fluoride
1
PotassiurnChlo~de
-
.
-
---
KC1
HydrogenChloridr"C1
Calcium Chloride
.- ..- --.
1
CaCI2
1
( Potassium Fluofide I
j Hydrogen Fluoride j
I Calcium Fluoride I
mi
CaF2
~
Comparing the properties of Fluorine and Chlorine
Fluorine and Chlorine react
with metals
I
Methodology
- - ..- -.- -.
E,rplainitzg the reaction between Sodium and Fluorine
1 Sodium + Fluorine 3 Sodium Fluoride
2Na +
F2
3 2NaF
E.xpl(ur~ulgrile r-eactiori between Sodium and Clzlorine
--
( Sodium + Chloride 3
Sodium Chloride
I
L)e\$c~lor~rzg
the concept (Clo) about the nature of properties of
f71zro/.rrleatltl Chlorine based on F,, Fz, F3 and Reactions ( I )
(lt?f/ ( 2 )
/ -- --
Fluoririe and Chlorine show
Ellcournging to find out the reason for Group 17 elements
showing similar properties
Recnllirig the corlcept of valence electrons and their role
in cllemical reaction
A.
phase 1
9
--
~
v
f'rovirie opportunity to find out the electronic configuration
/
number
1
I
Name Of
Symbol
the element
(
Electronic configuration
-
35
53
85
1 Iodine
I
Astatine
2, 8, 18, 1
I
At
u
I(ier~rifi~ing
..
the reason for showing similar properties by halogens
All halogens have same number of valence
electrons (7). So they show similar properties
- -...
Developing the Cbncept (CIJ about the nature of valence
e1ectt.on.s in the atorns of elements in the same group.
-,'
Atoms of elements in the same group of
the periodic table have the same number
of valence electrons
Encouragzrzg students to go through the table given below,
slrotr~rtlgthe t.eactlvity of halogens as we go down the group.
Halogen
Rromine
idin.
Conditions needed for
reactions to occur
1 1
Heating
i i
1
Reaction
Reaction Occurs
Strong Heating React very slowly
--
- -
--
Methodology
Developing the concept (C13 about the reactivity of halogens
dowtl tlie group
The reactivity of halogens decreases as we
go down the group (Example: Fluorine is the
first element and Iodine is the last element)
Identlfjing the most reactive halogen
..<
I---
\
--
1
7----
'.
Fluorine is the most
..
'o~en
Atoms of the same group
contain the same number
of valence electrons
Elements in the same group
show
similar
chemical
-.
-
.
Methodology
-
171h group elements are halogens.
Halogens are reactive non-metals
Halogens have seven valence electrons.
Halogens show similar properties.
.- ---
/
//'
,/ Scientific Terms / Concepts
HALOGENS
I
FLUORINE
CHLORINE
.
BROMINE
IODINE
Methodology
CONCLUSION
'The Group 17 elements in the periodic
table are called halogens and they are Fluorine,
Chlorine, Bromine, Iodine and Astatine
1
/ZI
(
I
EVALUATION
Fill in the blanks.
(1 ) Seventeenth Group elements in the
Periodic Table are called ----( 2 ) Halogens contain ---- valence
electrons.
1I
( 3 ) First element among the Halogen
group is
1
I
j
11 ,411swerthefollowing:
( I ) Name the Halogens.
t 2)
Halogens show similar properties.
Why?
I
A
(3) Name the most reactive non-metal.
--
-
Methodology
.
UNIT 12 TRANSITION ELEMENTS
.
--- -.
-
Learning Point
'l'he elements in groups
3-12 in the periodic table
are
called
transition
elements.
-
-
~
~
..~
~-
PREVIOUS KNOWLEDGE
.
1'1~ovlde opportunizy to go through the figure 4.9
i.c~pi-esei~ting
the arratzgenlent of elements in group 3-12
lu~.\cd 0 1 1 atottuc nur~lber..
n
.
-
21
~
~~~
22
,
39
~~
~
57
1
23
l
-
24i25
26
27
28
29
30
44
45
46
47
48
76
77
78
79
80
108
109
-
40
41];2713
72
71
75
(Atoniic numbers from 21 are given in the columns)
Fig. 4.9 Arrangement of elernents in group 3-12 based on atomic number
-
--
-
-
Methodology
TRANSITION ELEMENTS
Periodic Table(PT-5)
Students are encouraged to answer the following questions with the
help of' Figure-24 and PT-5.
I . I low many groups are there in the
'I ransit~onseries?
2. Name the groups belonging to Transition series
3. Where is the position of Transition elements?
4. I low many 'Transition series are
fhere in the Modem Periodic Table?
5 . Name some Transition elements
................
................
................
................
................
--
-
-
-
- --
- -.
Methodology
Developing the facts Fd, Fs,F6 and F7
re are 10 groups in the Transition Series
(/;ransition
I
elements comprises of groups 3-12
ransi sit ion elements lie between group 2 and
group 13
F
There are 4 transition series
(
Stutletzts are encouraged to identifi common transition
elenlc~tltswit11the help ofperiodic table (PT-5) and suggest the
itn[~o~.ftrr~f
uses c?ffurniliar metals.
I
Iron (making weapons), Mercury (thermometer),
Gold (ornaments), Silver (ornaments), Tungsten
I
.
-
-
--
-
-
Methodology
E~~couruging
to answer the following questions
1. Name five metals.
2. How many complete series are there in the transition
ser~es?
3. l low many members are there in the first transition
series'?
4. How many members are there in the second transition
series?
5. [low many members are there in the third transition
series?
6. Name the elements present in the tenth group.
7. Locate the position of Iron in the transition series.
8. Name the hmiliar elements from the first transition
series
9. Name the liquid metal.
De\selopirlg the Concept C13about Transition elements
Trarzsition elements are metals
Transition elements are metals
Elements belonging to groups 3-12 are
called transition metals
__---
,
,
/
-
Scientific Terms / Concepts
I/
\,I.
-
TRANSITION ELEMENT
\--
The elements in groups 3-12 in the
/I
periodic table are called transition elements
,-i---
EVALUATION
11
I
Atlswer- the following.
What are transition elements?
( 2 ) Name the liquid metal.
( 3 ) Name two metals used for making
ornaments.
(4) Name two transition metals used for
rnaking electrical cables.
(5 ) Name the transition metal used for
making filament of lamps.
(
1)
I
-.--
--
-
-
-
Methodology
UNIT 13 GROUP NUMBER AND VALENCE ELECTRONS
--
-
-
-
- -- --
Learning Points
In Group 1 and 2, the number of
(i)
valence electrons is equal to
group number
( ~ i ) From the groups 13 to 18,
number of valence electrons is
equal to group number minus 10
\
-
- -- .PREVIOUS KNOWLEDGE
-.. -- .
-
- --
-
G
Students izmve learnt the electronic configuration.
1Vr-iting tlie electrorzic configuration of Group 1.
-
-
-.
Methodology
-
Efectrorric Corrfiguration of Croup I
--
-
-~~~
Electronic
Configuration
-.
~
-.-~,
~~
tlydsogen
No. of
Valence
electrons
~-
~
1
I
1
-
~~
~
Sod~u~n
1
1
-
1
Rubedtum
2,8,18,8,1
1
2,8,18,18,8, 1
1
2,8,18,32,18,8, 1
1
~
('aest urn
. ~ .
~
L ) ~ ~ , , , i ~ p1i 1) 1l gc,o)lcept
~
CI4about number of valence electrons
111
(;~.oi/pI d e t ~ c ? ~ ~ t s
c,,;
~
~
'11 ~ r o iqeiemertts contairz 0.e
.
. ,,, valert ce electrort .
. _
_
I'tiiting tile electrortic configuration of Croup 2
...
I
~
Element
---
... .
electrons
De~jc~lop
/he c,orlc.e;r,t C I Subout tzurnber of valence electrons in
AN Group 2 elements contairr two
,
-- -
valerzce electrorts
Methodology
CVritit~gtile electronic configuration of Group 13
.
-
i
)
- ---
Electronic
[LIement
Boron
--
. .-
--
-
1I
Ciailium
A3
.
Alurnin~um
-
electrons
1
1
2,8,3
~
31
2,8,18,3
.. .
2,8,18,18,3
Indium
~
~
~
2,8,18,32,18,3
'l'hallium
-
-
1
Develo/~it~g
tile cotzcept C16 about the nutnber of valence
Group Nunrber(l3) - 10
Valence electrons(3)
= Number
">
of
-
- - ..--
.
the electronic configuration of Group 14
Etlcolo.r~gesto write
-
--
Hement
No. of
electrons
Electronic
Configuration
No. of
Valence
electrons
6
2,4
4
14
2,8,4
4
32
2,8,18,4
4
50
2,8,18,18,4
4
2,8,18,32,18,4
4
~tp--
..
('arbon
+
'
Silicon
~
Methodology
-
.- .
~
(iermaniurn
~
~
p
~
-
~
I ,cad
----
-
p
L
-
~
82
~
Dc\~clopitlgtlze corzcept CI7about the number of valence
c1ec.ti.or1.sr t ~(;I-oup 14 elernerzts
Group Nurnber(l4) - 1 0 = Nurrrber o f
,
Valence electrons(4)
\
%\
--
El~cozrrcrgrsto write
I Element
I
the electronic configuration of Croup 15
Electronic
I
electrons
-~
i
~~
i Nitrogen
Arsenic
-
-
{--T&i%3+4
1)c~l~c~lopitzg
the concept Clg about the nurnber of valence
c.lec,(~.on.sill C;/.oulp15 elernents
Group Number(l5) - 10 = Number of
,,
Valetice electrons(5)
-
@
,I,I
-
Methodology
--
-
ACTIVITY (
Eticolo.~~gtls
to write the electronic configuratiori of Croup 16
1
Electronic
Element
---
&~~
-
-
Sulphur
I
1 Selenlunl
TF261
2,8,18,6
l>cvcloping tllr c.oncept C I 9 about the rlurizber of valence
c~l~~c,r~.oiis
it1 G'rvup 16 elelnents
-.~~
fi,'>,9\
/
\>-... -.
~-
Group Number(l6) - 10 =Number of
Valence electrorrs(6)
-...
1
.
-
Etico~rrc~ges
ro write the electronic configuration of Group 17
1
Element
No. of
electrons
:
Fluorine
1 9 i
Electronic
Configuration
277
1
1 7 1
No. of
Valence
electrons
Bromine
I
.-
,
I
2,8,18,18,7
lodrne
I
,
Astatine
~
85
2,8,18,32,18,7
-~
-~~
,
~
1~c~~~c.loping
tlie concept CZ0about the number of valence
c~lc~.ri.otl.s
ill G~.oup1 7 elements
,
.
.---.---
Group Number (I 7) - 10 = Number of
,)Valerrce electrorrs(7)
-...
-
.
-.
Methodology
- -
E~~c,olrt.trge.s
to write the electronic configuration of Group 18
n
No. of Valence
electrons
I)c~\,eloprrzgtilt.' concept CI1about the number of valence
Group Number(l8) - 10 =Number of
Vale~zceelectrons(8) except for
\
Neliunt (F1
Irl~n/~/\.rng
the r-oliltion between Group number and number
c~vc~lerrce
electrorts (based on concepts
C,q
to CZ,)
(;roup Number = Number of Valence electrons
(;roup Number - 1 0 = Number of valence electrons
.-
-
Methodology
--..
a
All elements in group 1 contain only 1
valence electron.
All elements in group 2 contain only 2
valence electrons.
All elements in group 13 contain only 3
valence electrons.
All elements in group 14 contain only 4
valence electrons.
All elements in group 15 contain only 5
valence electrons.
All elements in group 16 contain only 6
valence electrons.
All elements in group 17 contain only 7
valence electrons.
All elements in group 18 contain only 8
valence electrons except Helium (Helium
has 2 valence electrons)
-
1
1I
-
.
Methodology
-
(I) In Group 1 and 2, the number of
valence electrons is equal to group
number.
(2) From the group 13 to 18, number of
valence electrons is equal to group
number minus 10
/
_I
.
\
EVALUATION
1
/
1
I
the follon~ing:
.~,Is,v~Y
( I ) How
many valence electrons are there in
group 1 elements?
(2)An element X belongs to 1 3 ' ~group. How
many valence electrons are there in it?
(3)An element contains 6 valence electrons.
'To which group it belongs?
( 4 )1 low many valence electrons are there in
group 18 elements?
(5)Name the element having only 2 electrons
In the group 18.
-
-
Methodology
..
UNIT 14 PERIOD NUMBER AND NUMBER OF SHELLS
Per~odNumber represents the number
of'shells in an atom
~
PREVIOUS KNOWLEDGE
~.~
- ~ -
.Ctrrtients lruve learned the electronic cor$guration of
c~lotnentsirnti provide opportunity to recall the concept
of period.
Etlc,orrt.ilge studrvlts to wvrite the electronic configuration of
periotl 1
\k't.iting tlre electronic cotzjiguration of Period I
-
.~
Hydrogen
lilen~ent
1
N o . of electrons
1
Electronicp--~.p-.- o n f i ~ u r a c o n
1
N o . of Sl~ells
-~
~
~-
~
-
~
~
-
~~
-~
~
p
~
~
Helium
2
2
1
-
--
. --
Methodology
Developing tile cotzcept C22about the number of shells in the
j i r l ~ tp e r i o ~eletnents
i
First Period elements contain only
--__-- -
Enco~ri.rigesto wrlte the electronic conjiguratiori of Period 2
Dcl,c,lo/~rtlgthe corlcept Czj about the rzul~lberof slzells irz the
.scc~otrclper-iotl elerner~ts
--
Second Period elemerzts corztairz
two slzells
'-__-_-
I:'rlcolr/.c~ges
to write the electronic corlfguratiotr of main group
clerricrit.s in Period 3
--
-
-
-
--- -
Methodology
-----
I)ellc~lo/)~ng
tile csoncept Czd nbout the nurnber ofslzells in the
t11it.il/~c,r.iodelrt~renrs
~
-
~
~
Tlrird Period elemerzts corttairz tlzree
sltells
\
,,
----
Enc,o~rt.trgesto n,r.,fe tile electrorric corrjiguratiorz of rnain group
elerrrerrts irr Period 4
.
I
~~
-
ri
i
i
~p~
E
c
Elerneut
m
i
.
n
m
-.
CI
3
~
~
~
.
.
. ..
20
19
No. of electrons
II
--
31 3 2
33
34
35
36
P
,
N
"0
N
,
"!
Oe
"
N
L
,p
. .
Electronic
('o~~liguration
-
"
h
m,
L
"
z
G
"
t
,
v
Z
l
W
,
Z
,
_oo
P
L
o\
4
w
4
4
4
-
No. o f Shells
-
*P
"00
ern
4
-
.. .
..
4
4
4
-..
!J)~'l'~'/O/llllg
tllc. c,oncept Czsnbout the nurnber. of shells in the
,
.
~
Fourtlz Period elemerzts contaiit four
-
[I 01 ACTIVITY (
l:'~lco~o.r~ges
to write the electronic conjiguration of main group
elernerrts irr Period 5
0
Y
5
-.--
No. of
3 7 3 8
electrons
i
~~~
~~
4I 9
50
5
52
53
54'
- .~~.
Eiectronic
L
3
3
L
3
O0
"O0
-1
00
3
ti011
L
c.
VI
"
QI
No. of
/ Sliells
5
5
5
!
!
L)c>\~c~lol~r~~g
the cotlcept CZnabout the nunzber of shells in the
. / ~ / I / I p ~ ~ . r oeleuteizts
d
-.--
Methodology
-
-
--
Eticout.czges to wrrtr the electronic configuration of main group
r1rn1c.rrt.sirr
Period 6
r i
--
~
a
C
3
i
-~
~
~
No. ill.
,.w
N
"
Electronic
Contigur
W
3
u
Q
3
"
ation
SO0
"
n
L
UP
"00
"
"N
"
00
"
W
"00
-w
"u
83
82
J
n
"'J
L
"
W
P
L
84
"
N
U
O0
P
L
"C
w
"
"O0
"
N
"O0
W
"!
"
W
w
"
"
n
01
n
"a
86
85
L
W
"
L
4
No. o f
' 6
Sllells
W
"hJ
L
"w
w
~-
~
6
I
/ j ( ~ ~ ~ , l o tlze
p l t C~ Og J I C ~ CZ7
~ I about the nunlbe~
of shells
\
"w
L
"w
-
~-~~
~
O
"0
L
.
81
56
55
elecrrons
in the d
r utlr /)c~t.rotlcieriletzts
,
i<',c>, Sixtlt Period elements contain sir
\
--
-
~.
-
Methodology
Iderltlfyirtg the relation between period number and number
of slrells. (Based on the concepts C22-C27),
Period Number represents the number of shells
preset in an element
First Period elements contain only
1 shell.
Second Period elements contain 2 shells.
Third Period elements contain 3 shells.
Fourth Period elements contain 4 shells.
Fifth Period elements contain 5 shells.
Sixth Period elements contain 6 shells.
Seventh Period elements contain 7 shells.
Methodology
-
1 1-
~
~
.-
Period Number represents
number of shells in an atom
I
the
I
EVALUATION
1 Atrrwer thefollowing que.stions:
( 1)
How many shells are there in the elements
of Group I ?
(2) How many shells are there in the elements
of Group 2'?
(3) Name the group to which the element
belong:.
(I)
Havlng 2 shells
(11)
Havlng 5 shells
(111)
Hav~ng3 shells
(4) What is the relation between the No. of
shells and the Number of the Period?
I
Methodology
-
-
ATOMIC SIZE DOWN A GROUP
UNIT 15
Learning Point
Atom~c size increases from top to
bottom
in
a group due to increase in
number of shells
..
~
~
~
PREVIOUS KNOWLEDGE
Students are encouruged to recall the following
c'otzcepls
J
Atom~csize 1s related to atomic radius
J
['he elements in a group contain same valence electrons
J
K-Shell can accommodate 2 electrons
J
L-Shell can accommodate maximum of 8 electrons
J
M-Shell can accommodate maximum of 18 electrons and
SO
on.
-
Methodology
-
-
DlSClJSSlNG THE CHARACTERISTICS OF A GROUP
Studetlts are encouraged to write down the electronic configuration
of Litlrium to Francium. (with the help of Periodic Table)
Li
11
j Sodiurn
Na
19
1 ~otassiurn
K
I
Rb
Cs
Fr
--.
...
2, 8 , 8 ,
OUTDOOR ACTIVITY
/
I
/'
/'
/'
Sevetl students of Standard IX are
~tzcouragedto prepare display cards
I
( N represents nucleus of an atom) and the
rest of'the students to prepare display
cards showing
9
\\
represents electron). Students carrying
tiisplt~ycard N and that of e are asked to
(
\
I
I
-
-
- --
Methodology
-.
--
The ./ir.st student carrying display card N and the first one
carr,xirlg display card 'e' were selected and encouraged to
rot-tn t l ~ structure
r
of Hydrogen atom.
(-$
Hydrogen
..a.
.*
.......................
.
I
.I
@......
*.
..a.
-1.
..
..............e..
..
....
....
-
..
Methodology
--
The second student carrying display card N and the next three
carr:ln1g display card ' e ' were selected and encouraged to
forrw tile structure
Lithium
of
Lithium atom.
.............................
....
..'
.. ...I
...
..*.
..............
...
....
.........
*.
....
.......
....
......................
..
I.
.-
-
--
...
Methodology
The t11it.d student carrying display card N and the next eleven
crrrr? rng cilsplq card 'e ' were selected and encouraged to
fotwl tlre rtrurtur-e of Sodium atom.
Methodology
-
7'/7efourth student carrying display card N and the next nineteen
carr~~ing
r l ~ ~ p l acard
y 'e' were selected and encouraged to form the
strt1ctlrr.e of Potassium atom
L)e~,c,lo/~
the
cvrlcept Czsabout the relation between the size o f
the ritor?~ar~drzztrnber of shells (based on activity I to 4)
Size of the atom increases with
increase in number of shells
-
-
.-
-
--- .-
--
227
-
-
- - - - - .-
Methodology
Studetrts are encourczged to draw the Bohr model of Hydrogen,
Litlliutrl, Sodiutn, Potassium. Rubedium, and Caesium
,-.
(1)
i
I
!
It
Hydrogen
~-
~
Lithium
Methodology
--
~
..
-
~
Potassium
-- - -
---
.
.
-
-
Methodology
--
Caesiurn
..
-
Methodology
-
- --
- --
Methodology
Develop tile cotrcepts Crs to C33ahout clzange in atomic size
tlo,c,ir flrr gi.o~cp
-.
Tlze Number of shells in an atom
irzcreases as we move dowrr the group
The size of the atom increases as we
\
.
move down the group
._
/
Tlze size of the atom i~zcreasesdue to
irrcrease in number of shells
Tlze f i s t elemerrt is tlze smallest atom
The last element is the biggest atom
in tlre group
'-----
--
-
-
---
-
Methodology
Atomic size increases from top to bottom
Number of shells increases from top to
bottom
In a group, atomic size increases due to
increase in number of shells
In a group, first element is the smallest
In a group, last element is the biggest
<
---.
,
I
I,
i
\
Scientific Terms / Concepts
ATOMIC SIZE
,
\.
--.
l~..
\
-I
@
CONCLUSION
Atomic size increases from top to
bottom in a group due to increase in
number of shells
/ 4nswer thefollowing:
I
( I ) How many shells are there for elements
in the first period?
1
I
I
I
(2) tiow many shells are there for elements
in the second period?
(3) How many shells are there for elements
in the nth period?
1
I/
(4) Name the smallest atom in the first period
( 5 ) Name the biggest atom in the second
period
(6) What happens to the size of an atom as
el---
we move down a group? Why?
I
1
UNIT 16
-
ATOMIC SIZE ACROSS A PERIOD
--
-
F
Learning Point
Atomic size decreases from
left to right in a period due to
increase in the nuclear charge
without
~ncreasing
the
number of shells
L
-
-
PREVIOUS KNOWLEDGE
~
~
I'r-ovidr opportunity to recall the following concepts
Atomic size is related to atomic radius
J
'l'he elements in a group contain same valence electrons
J
K-Shell can accommodate 2 electrons
J
1,-Shell can accommodate maximum of 8 electrons
u
M-Shell can accommodate maximum of 18 electrons and
so on.
--
.-
-
-
-- -.
--
Methodology
DISC'bSSING THE C7HARACTERISTICSO F A PERIOD
Stucient.~ are ~ncouraged to write down the electronic
cor2f;gurulion of Lithium to Neon with the help of Periodic Table
Element
Elenlent
Atomic No.
Electronic
<:u~itiguration
.-
~~~
~
--
-
-
-
Methodology
--
(OUTDOOR ACTIVITY)
/
/
/
/"'
T~'~ent.1,
five
students of Standard IX
clre erlcouraged to prepare display
c~ardssl~owingthe sign +
8
represents proton of an atom) atzd
atlother 25 students to make display
c a t ~ l sshowing the sign
rlisj~la,~
card + and that of - are asked
Methodolow
1 1 ACTIVITY (
The first three students carrying positive cards are asked to
keep their positions inside the first circle which represents the
nucleus of' Lithium atom and three students carrying negative cards
are asked to take their positions outside the circle in the order 2, 1
respectively in the 2"d and 31d circles which represent the first and
second s ~ ~ c lrespectively.
ls
Three pieces of rope are taken and one
end of each rope is tied to the students carrying negative cards.
.file tree end of each rope is given to students carrying positive
cards and are asked to pull the string with slight force towards the
centre
Lithium (2,l)
--
--
- -
-
Methodology
1[]1 ACTIVITY (
'I'he next four students carrying positive cards are asked to
keep their positions inside the first circle which represents the
nucleus of Beryllium atom and next four students canying negative
cards are asked to take their positions outside the circle in the order
2, 2 respectively in the 2ndand 3rdcircles which represent the first
and second shells respectively. Four pieces of rope are taken and
one end of each rope is tied to the students canying negative cards.
The lrec end of each rope is given to students canying positive cards
and are asked to pull the string with slight force towards the centre.
Beryllium (2,2)
- .
-
- --
--
Methodology
11I ACTIVITY (
The next five students carrying positive cards are asked to
keep their positions inside the first circle which represents the
nucleus of Boron atom and next five students carrying negative
cards are asked to take their positions outside the circle in the order
2, 3 respectively in the 2ndand 3rd circles which represent the first
and second shells respectively. Five pieces of rope are taken and
one end of each rope is tied to the students carrying negative cards.
'l'he lree end of each rope is given to students carrying positive
cards and are asked to pull the string with slight force towards the
cent1.e.
-
-
.-.- --
-
--
Methodology
-
01( ACTIVITY
(
The next six students carrying positive cards are asked to
keep their positions inside the first circle which represents the
nucleus of Carbon atom and next six students carrying negative
cards are asked to take their positions outside the circle in the order
2, 4 respectively in the 2ndand 3rdcircles which represent the first
and second shells respectively. Six pieces of rope are taken and
one end of each rope is tied to the students carrying negative cards.
The free end of each rope is given to students carrying positive cards
and :IIC asked to pull the string with slight force towards the centre.
.- .-
-u
--____--*
Carbon (2,4)
~
~
~
..
Methodology
~
~
The next seven students carrying positive cards are asked to
keep their pos~tionsinside the first circle which represents the
nucleus of Nitrogen atom and next seven students carrying
negatlve cards are asked to take their positions outside the circle in
the order 2, 5 respectively in the 2ndand 3rdcircles which represent
the first and second shells respectively. Seven pieces of rope are
taken and one end of each rope is tied to the stud.wts-carrying
negatlve cards. The free end of each rope is given to students
carrying posltlve cards and are asked to pull the string with slight
force towards the centre.
Nitrogen (2,s)
.-
--- -
242
--
---
-
. -
Methodology
--
01[ ACTIVITY
(
The next seven students carrying positive cards are asked to
keep the~rpos~tionsinside the first circle which represents the
nucleus of Oxygen atom and next seven students carrying negative
cards are asked to take their positions outside the circle in the order
2, 6 respectively in the 2"dand 3rdcircles which represent the first
and second shells respectively. Eight pieces of rope are taken and
one end of each rope is tied to the students carrying negative cards.
The tree end of each rope is given to students canying positive
cards and are asked to pull the string with slight force towards the
centre
.
-
~
-~
-
Methodology
~
Developing the concept
C;4
to Cj6.aboutthe change in atomic
size trc,ross a period from Activities I to 6)
( 5 - ; L e a r attraction increases along
a period
\___
/
'<-\
0
--
Number of shells remains the same along
aperiod
Size of the atom decreases from leji to
right along a period
--
- -
-
Methodology
Students are encouraged to draw the Bohr model of Lithium,
Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine and Neon.
Developitzg the concepts ubout the reason for decrease in size
(f~ f o l i ~i C Y O S SN period
(7
,;/--,
\
c
.
3
7
(C2y37to CdO)
iVuclear attraction increases along a
period
\-/
Number of shells remains the same along
\_--
,------.
,/';-7
Size of the atom decreases from left to
( ( c.39 )
\ c ~ , . , / right along a period
1
.
/----
"
\'
Number of protons increases with number
- .
-
--
Methodology
--
-
-
Number of shells remains the same in a period
Nuclear attraction
increases
on
outer
electrons
Atomic size decreases from left to right in a
period.
11
First element in the group is the biggest atom.
1 ~ selement
t
in the group is the smallest atom.
a
-
-
17dT
n
(:ONLI.IIYION
s
1
( (
Atomic size decreases from left to
right in a period due to the increase in
nuclear charge without increasing the
number of shells
-
EVALUATION
--
I.
I1
--
-
--
--
--
Name the smallest atom in the second
period. Why is it so?
2. What happens to the size of the atom as
we move from left to right in a period?
3. Potassium is the biggest in the third
period. Why?
I
-
Methodology
( TEST YOUR KNOWLEDGE
7-
\
(I) Name the following:
(1)
The scientist who designed the Modem periodic table
( 2 ) The scientist who first made a successful attempt in
classifying the known elements
( 3 ) The smallest atom
(4)
I'he biggest atom
( 5 ) 'I'he shortest period
( 0 ) The longest period
( 7)
rhe incomplete period
( 8 ) Number of'periods
0 ) Nu~nberof groups
( 10) Another
name of First group elements
(
I I ) The first element in the Group I
(
i 2 ) The last element in the Group 1
(
13) 'The first element in the Group 17
(
14) The first element in the Group 18
( 15 ) A
group of metals
( 16) A
group non metals
(11)
Define the following:
( I ) Ciroup
( 2 ) Period
(3) Modem period~cLaw
( 41 Mendeleev's Periodic law
(5 )
Transition elements
(111) Answer the following questions:
(I)
What happens to the atomic size as we move down the
group'! Why'?
( 2 ) What happens to the atomic size as we move from left
to right in a period? Why?
( 3 ) Where is the position of transition elements in the
periodic table?
(4) Where is the position of actinides and lanthanides in the
Periodic table'?
( 5 ) Where on the periodic table would you find
(i)
Metals
( i i ) Non metals
(iii)
l'he alkali metals
(iv) Halogens
Methodology
~-
I . Why was Mendeleev more successful with his
Periodic Table than Newlands?
2. Compare Modern Periodic Table with Mendeleev's
Periodic Table
3 . What are the main characteristic features of Modem
Periodic Table?
4. Prepare chart of MODERN OERIDIC TABLE.
5. Prepare an album including the contributions of
Lavoisier,
johns
Newlands.
Dobereiner,
Dmitri
Mendeleev and Moseley.
6 Draw the main groups (1, 2, a n d l 3 to 18) in the
Modern periodic table.
(I 1
L . R.L)aniel, R. G. Scott and E. M. Edward (1993). Cltemistry-
Principle and Practice. USA: Saunders College Publishing.
(2)
R. M.Gallagher and P. lngram. (1994). Cltemistry. Oxford: Oxford
I lriiversity Press
(3)
li. M.Gallagher and P. Ingram. (1996). Cltemistry made clear.
Oxford: Oxford University Press
(4) 1'). Garvie. K. John and A.Robertson (1993).
Core Cltemistry.
Oxford: Oxford University Press.
(51
H. Harrow (1927). Emittettt Clternists of Our Time. Van Nostrand,
New York
I
( i . .]ones, M Jones and D. Acaster (1993) Clterrtistry. Cambridge:
('alnbridge Lniversity Press
(7!
('.N . I<.
Kao
(1 999)
Understanding
Cltentistry. Hyderabad:
I lliiversitics Press (India) Ltd.
(St
h1.H Kobcrt and James T. (1997). Science matters. Hyderabad:
I lnivcrsities Press (India) Ltd.
(01
.
R 'l'racy.. H.E. Tropp and A.E Friedl (1974), Cltentistry. Holt,
Ilinehart and Winston, Inc.
ACHIEVEMENT TEST IN CHEMISTRY
Std I Y
Time: 1 Hour
Max mark: 25
Instructions: Answer all questions
(I)
Choose the correct answer from the bracket (Each
question carries 1 mark)
(I )
(2)
(3)
(4)
(5)
The b~ggestatom is
(a)
Oxygen
(b)
Nitrogen
(c)
Fluorine
(d)
Helium
1 lalogens belong to
(a)
Group1
(b)
Group 2
(c)
Group17
(d)
Group 18
Which of the followtng is a transition metal?
(a)
Mercury
(b)
Magnesium
(c)
('opper
(d)
Iron
1 he incomplete period in the Modem periodic Table is
(a)
I
(b)
2
(c)
7
(dl
8
1 he number of valence electrons in the 1 6 ' Group
~
elements
IS
(a)
2
(b)
8
(c)
I
(dl
6
Methodology
- - --- ---
(6)
I'he electronic configuration of an element is 2, 8, 7. How
many shells are there in it?
(a)
I
(b)
2
ic)
3
(dl
7
( 1 x6=6marks)
(11)
Find the odd one
(I )
Lithium, Strontium, Sodium, Potassium
(2)
Potassi um, Calcium, Aluminium, Copper
( 3)
C'hlorine, Oxygen, Nitrogen, Magnesium
(4)
Oxygen, Helium, Nitrogen, Fluorine
( 1 x4=4marks)
( I l l ) Define the following:
(
I
)
(2)
(jroup
Per~od
(IV) State the Modem Periodic law
(V)
( 1 x 2 = 2 marks )
(2xl=2marks)
Nanie 3 transition elements and write their uses
( 3 x 1 =3marks)
(VI) ('ompare the merits and demerits of Mendeleev's
I'er~odic table
(3xl=3marks)
(VII) I,ook at the table and answer the questions given below:
'I'he b~ggestatom
The smallest atom
Atom with highest electro negativity
Atom with lowest electro negativity
Halogen
Alkallne Earth Metal
I rans~t~on
element
Number of electrons in the outermost shell of B
SCHOOL OF PEDAGOGICAL SCIENCES
MAHATMA GANDHI UNIVERSITY
KOTTAYAM
ATOMIC STRUCTURE
(STANDARD IX)
Prepared by
Supervised
RAJESWARI. K
:
Dr. EXEMMAL. J
(Supervising Teacher)
Reader
Departmerrt of Education
U~riversiqof Kerala
--
Remedial
Methodology
-
Teaching
Materials
on
the
topic
ATOMIC S'TRUCTURE is subdivided into 11 Units.
1)etails are given in pages 255-334. In each Unit, students
are provided chances for observation, classification,
~dentification,discussion, analysis and concept formation.
Suitable charts, models, examples, illustrations, life
situations
are
also
used
for
developing
new
conceptsiteaching points. Practice session is given at the
end of' each unit to test the level of attainment of the
students. Extended Activities and Reference Section are
An Achievement Test on Atomic Structure is
given.
siven at the end of the material.
~
-
--
-
-
CONTENTS
UNIT 1
CONCEPT OF ATOM
UNIT 2
PARTS OF AN ATOM
UNIT 3
NUCLEUS OF AN ATOM
UNIT 4
ELECTRIC CHARGE OF PROTON,
NEUTRON & ELECTRON
UNIT 5
CONTRIBUTIONS TOWARDS THE
DISCOVERY OF ATOMIC PARTICLES
UNIT 6
SHELL OR ORBIT
UNIT 7
CHARACTERISTICS OF ELECTRON
CLOUD
UNIT 8
RELATIVE MASS OF FUNDAMENTAL
PARTICLES
UNIT 9
ATOMIC NUMBER
UNIT 10
MASS NUMBER
UNIT 11
REPRESENTATION OF AN ATOM
--
-
-
-
- --
-
-..
Methodology
-
INTRODUCTION
The first definite theory about the structure of
matter was put forward by English Scientist and School
I'eacher, John Dalton (1808). According to Daltons
atomic theory matter consists of small indivisible
particles called atoms, which can neither be created
rror be destroyed. Atoms of the same elements are
alike irr all respects & combine witlz other atoms in
sirtrple wlrole number ratios forming compounds or
rtrolecules. Dalton's atomic theory remains undisputed
L I to
~
the end of 19th century & early 201hcentury showed
[hat the atom has a complex structure and is divisible.
7'Irese studies further revealed that the atoms are
divisible into smaller particles called protons,
rr rlrtrorrs and electrons. Tlzese particles are regarded
us furrdant erttal particles because tlr ese are tlze
rrrairi cotrstituerzts of all atoms.
L
-
-
-.
-
-
-
- .
- .
Methodology
' Learning Points
~.
~~
'I.
I
Atoms are the building blocks from which all the
: materials in the world are made up of
2
i Every atom has a nucleus at the centre and electrons
I outside the nucleus
3
Nucleus is the central part of every atom which consists
of protons and neutrons
Protons have positive charge and electrons have negative
charge. Neutrons are electrically neutral
The fundamental part~clesof an atom are discovered by
sc~ent~sts
such as J.J. Thomson, Earnest Rutherford and
James Chadwick
1 he path of an electron around the nucleus is called shell
or orb~t
6
.~~
7 Electron cloud is the part of an atom in which there is
possibility of finding electrons
~
/
~
8
Relative mass of neutron, proton and electron
9
Atom~cnumber is the number of protons in an atom or
number of electrons in a neutral atom
. j
..
/ Mass number is the total number of protons and neutrons
10
-<
II
--
~
~~
~
Atoms can be symbolically shown using atomic number
: and mass number
1
--
--
-
-
-
-
-
Methodology
LET US THINK AND
UNIT 1
--
- --
CONCEPT OF ATOM
-.
Learning Point
Atoms are the building
blocks from which all the
niaterials in the world are
made up of.
--
-
PREVIOUS KNOWLEDGE
-- -- --
Students at Secondary level might have learnt
that all
inaterials are made up of matter and the Fundamental unit of
matter 1s the atom Molecules are formed by the combination of
atoms
Students are also aware that substances differ in their
propet ties due to the different type of atoms present in them.
Students are encouraged to think of twenty six letters
in the Etzglish Alphabet and the number of words that can be
developed by different combinations of the twenty six letters.
I
1 Each type of arrangement of htters make
i difierent types of words.
Fig. 4.1 1 Different words from letters
Etzc,our.r~gestudents to compare the letters in words with tiny
porticYrs
itz
suhstnrrces.
//'
/'
Words are composed of letters.
Similarly substances are composed
of simpler particles called atoms.
(
'\\
\~-.\
__Z
-
--
Methodology
--
Students are given a set of match sticks and are
encour.aged to develop dvferent Geometrical patterns using
matcl~sticks.
--
J
Fig. 4.12 Different Geometrical patterns from match sticks
-
-
-
-
-
Methodology
.
-
Encou~.agesstudents to make the following comparisons.
( I ) Letters- Word
(2) Match Sticks Geometrical Pattern
(3) Chalk Particles-Piece of Chalk
with
Atoms-Substance.
---\
,
'-
Substance
(matter)
Atom
\
/'
'.. L---
L,etters
t
a
n
Word
-..
Match Sticks
1-
-
I
Chalk Particles
~
-
.
- -~
p
~
Pattern
0 Piece of Chalk
~
L)e\>c.loprngthe concept about co~zstituentof matter
-.-
/--,
Atoms are constituents of all matter
-
-
-
-
Methodology
.
Disctl.ssing details about the discovery of atom by Sir. John
Daltorr (1 766-1844)
weaver. was born in Cumberland,
England. He began h ~ slifelong
career as a teacher at a village
schooi when he was only twelve.
I
Fig. 4.13 John Dalton
----
Seven years later he became a school principal. From his early
years to his death, Dalton carefully recorded the meteoric data
1 each day temperature, pressure, time, amount of rainfall and so /
forth. Dalton suffered from protanopia, an inability to
distinguish colours at all. Much to his amusement his sight
defect became known as 'Daltonism'
Dalton put forward the
atomic theory in 1803.
\.--.
b
-
According to John Dalton all matter is made up of tiny
I particles called atoms and atoms can neither be created I
nor be destroyed. Atoms combine to form molecules.
-
- -
- -- ---
-
Methodology
-
-
Atoms are constituents of all matter.
1
I
Atoms are the building blocks of all matter.
/
\\
/
'
Scientific Terms / Concepts
-ATOM
'.
--\
\-
-Q
CONCLUSION
Atoms are the building blocks from
which all the materials in the world are
made up of.
J
Id/
Atlswer
(I )
EVALUATION
thefollowing questions:
1
Define an atom.
( 2 ) Name the scientist who discovered that
all matter is made up of atoms.
( 3 ) What are the contributions of John
blton?
j
- .. . .-
UNIT
--
-
-
2
Methodology
PARTS OF AN ATOM
-
--
f
Learning Point
kvery atorn has a nucleus at
the
centre
and
electrons
outs~dethe nucleus
~ - , - ~
~~
1
'
-
i
PREVIOUS KNOWLEDGE
p-~
r
o
7-
t opportu?zif)~to recall that atonzs are the
c~or~stit~rents
of all i1zatter.
Stlrderrr.~rrre provided opportunity to recall that the sun is the
cetlt1.e of [lie solnr s,,,steirland the planets and satellites are tnoving /
1-evo11~irrg
illr .SUII rhrougl~somefixed path.
--
Methodology
.~
Fig.4.14
Solar System
Comparing atom, nucleus and electron cloud with solar system,
sun and planets and satellites respectively.
~
.~
~
'
\
Planets and
Satellites
Electron
('loud
--
/'
~
~~
-~/'
-
-
-
-
-
Methodology
.J'tuderzts are encouraged to represent the parts of an
cltorlr.
Fig. 4.15 Parts of an Atom
I
N ~ l c l e u sis at t h e centre of the atom
llectrons are present outside the
1111clcus.
-
-
--
-
Methodology
.
,
~
/
Scientific Terms / Concepts
3'
-I1:
0;
--
---
CONCLUSION
Every atom has a nucleus at the
centre and electrons outside the nucleus
1
EVALUATION
I
.III.YVLEItile following:-
1
(I )
Name the central part of the atom
(2 I Name the outer part of the atom
(3 ) Define the following:
1
i
(I)
Nucleus
( i ~ )Atom
..-
-
-
- ---
UNIT 3
-
Methodology
NUCLEUS OF AN ATOM
-
/ Learning Point
Nucleus 1s the central part of
ecery atom w h ~ c hconsists of
Protons and Neutrons
-- .- - ...
PREVIOUS KNOWLEDGE
f{rc,alling the position of nucleus and electrons in an
iltOlll
Discussirrg tlte cltaracteristics of Nucleus of an atom
Stude~tts are asked to draw a Circle using a
compass and lh& Mark the centre
-
.
-
(1)
Central
Part:(Nucleus)
Nucleus I S the central
part of every atom
I
-
(2,
-
-
..
1
Etymologically nucleus
means the central part NUCLEUS = CENTRAL PART
Neutrons and
Protons are
together
termed as
I
-
-
(5)
Mass of Nucleus
Mass o f the Nucleus is the total
mass of the protons and the
neutrons
Mass of Protons
+
Mass of Neutrons
Nucleus is the central part.
Neutrons and protons are present inside the
nucleus
Particles in the nucleus are called nucleons
Nucleus is electrically positive
1
Electrons are present outside the nucleus
/
/ Scientific Terms / Concepts
/"
/
i
NUCLEUS
PROTONS
NEUTRONS
ELECTRONS
,\
'\
\
NUCLEONS
--.
is the central part of every
1
I i atom Nucleus
which consists of Protons and
Neutrons
EVALUATION
I
( I ) Which is the centre of the atom?
1 (2) Where do you see the electrons?
1
1
1
I
(3 ) Where are the neutrons and protons seen?
( 4 ) Lkvelop models of nucleus for the
following atoms:
I
1
(i )
Hydrogen (No. of protons = 1, No. of
neutrons = 0 )
(11)
Helium (No. of protons
neutrons = 2 )
(~il)
Argon (No of protons
neutrons = 18)
=
2, No of
=
18, No of
1
I
--
UNIT 4
-
Methodology
-
ELECTRIC CHARGE OF PROTONS, NEUTRONS
AND ELECTRONS
-
--
-
-
,
\
Learning Point
Protons have positive charge
and electrons have negative
charge.
Neutrons
are
electrically neutral
--.
- -~
~
.
~
PREVIOUS KNOWLEDGE
~~
~-~
L51udent.sczre encouraged to recall the following concepts:
-1
Atoms are electrically neutral
_I
I- l o w of electrons causes electr~city
Methodology
. - -~ -.
- -
~
[[pcTid>
Students ure encouraged to compare the charges
of protons, neutrons and electrons from the Table (4.1) given
belotr,
Table 4.1 Charges of protons, neutrons and electrons
pr:i;t
Relative
charge
Charge
the
I
+1
1
1 Neutron
1 Positive charge.
1 Neutral charge
I Electron
/ Negative charge
I
-1
I
I
Protons have positive charge
Electrons have negative charge
=
- --
Neutrons are electrically neutral
-
Methodology
Q
CONCLUSION
(1)
1
Protons are positively charged
(2) Electrons are negatively charged
I
I
(3) Neutrons are electrically neutral
3
EVALUATION
--
Arisuver the following
1
questions:
( 1 )Name the positively charged particle in an
atom
I
( 2 )What IS the charge of an electron?
1
(3)Name the neutral particle in an atom
iI
(4)C'onrplete the table given below:-
Electrons
-.
Neutrons
---------
1
-
I
I
UNIT 5 CONTRIBUTIONS TOWARDS THE DISCOVERY
OF ATOMIC PARTICLES
Learning Points
'I'homson
discovered
electrons
( ~ i Earnest
)
Rutherford discovered
protons
( ~i )i James Chadwick discovered
neutrons.
--
--
-.
-
PREVIOUS
--
I'rovidlng opportunity to recall the contribzltions of
J J . Tllon~son.Ruthelford and James Chadwick
The existence of electron was first
demonstrated by J.J. Thomson in
1897.118 189 7 Ire discovered that in
ilre
atom
there
are
negatively
charged particles of low mass. He
I
called these particles Electrons.
.
Fig. 4.1 6
J.J. Thomson
Earnest Rutherford was born in
New Zealand in 1871. He was
working on radioactivity. In 1911
Rutherford's experiments proved
tlrat atoms contain positively
charged
particles
equal
in
magrritude to the charge oj
electrorls and mass greater titan
tlrat of electrons. He named these
pcrrticles as protoris.
Fig. 4.1 7 Rutherford
Irr 1911 Rutlierford's experiments showed the
esistrnce of a dense, positively charged centre, extremelj
srrrull wkerr compared to the total size of the atom. He
rrlrrrred this part as the nucleus.
Irr I Y32 Chadwick discovered that
crtorrrs corrtairt charge less particles
al.so. H e called these particles as
Nc,rrtroris. Its mass was found to be
nearly the same mass as that of a
proton.
Fig. 4.18
James Chadwick
.
.
.
Methodology
--
-
Electron was discovered by J.J. Thornson.
I'rotori was discovered by Rutherford.
I
i
( :hadwick
1
I-
discovered Neutron
~
.,
,
,/"
/' Scientific Terms / Concepts
J.J. THOMSON
RUTHERFORD
I
--.
-
/
-
-
- --
Methodology
p;
CONCLUSION
(1) J.J Thomson discovered electrons.
i
I
1i
(2) Rutherford discovered protons.
1
(3) James Chadwick discovered neutrons.
ia-
EVALUATION
Fill in the blanks
(I
)
I
I
Electron was discovered by------------
(2) Proton was discovered by-------( 3 ) ----was discovered by James Chadwick
/
( 4 ) The massive particles in an atom are-----
l
I
~~
-
~- -
UNIT 6
Methodology
-.
SHELL OR ORBIT
Learning Point
1
I'he path of the electron
around the nucleus is called
shell 01 orbit
- ...- -.
PREVIOUS KNOWLEDGE
-
-
-
-
---
Slucients iiiigllt have learnt that electron cloud is a region
\c,hrre clec,rrotis are found.
k;tzcc.)zrrclge the studerlts to draw the Diagrammatic
r.el)tc~.set~/ntior~s
oj-the stritcture of atoms of Hydrogetz (H), Helium
(tic),Litkirtttt (Li) atrd Sodiutn (Nu).
,
~
1
Hydrogen
(2)
1
I
Helium
I
j
Electron
!
Neutron
!
I
I
(3)
.
:
~
~
~~~
~~~
Lithium
Electron
Neutron
Proton
\
Methodology
~
,
-
I
.
- ---
Sodium
Electron
Proton
Neutron
Students
I
are
encouraged
to
compare
the
Diagrammatic
epl.csentatlons of' Hydrogen, Helium, Lithium and Sodium and
are encouraged to write the~robservations.
~
~~
Methodology
.-
Observations
n
The nucleus is at the centre of the atom
The nucleus conslsts of protons and neutrons
The electrons are present outside the nucleus
Electrons are present in the circular paths called orbits
or shells
Hydrogen has only one electron
The only one electron in the Hydrogen is arranged in
the first c~rcularpath
There are two electrons in a Helium atom
The two electrons in the Helium are arranged in the
same clrcular path
9.
'I'here are three electrons in Lithium atom
10.
The third electron in the Lithium atom is arranged in the
second circular path.
11.
'l'here are 1 1 electrons in thesodium atom
12
The first two electrons in the sodium are arranged in the
first c~rcularpath, the next eight are arranged in the
second c~rcular path and the eleventh electron is
arranged in the third circular path
-
--
--
Methodology
Encozonge stutlents to answer the following questions based
on tlrr observations
I . I 4hy
I S the
second electron enter in the first path itself?
1 he Flrst Shell can accommodate maximum of two electrons
-
2. W h y
3. Why
IS
the thlrd electron enter the second path?
IS
the eleventh electron not occupied in the second path
itself'!
Ucveluping the concept of electron shells
,
i
,
Electron shells are Circular path of
the electron outside the nucleus
lItrc,our.trgcto narne dqfeerent electron shells
-
-
-
_+--
/
,
_
!
.',
Electron Shells may be named
i
\
either
1, 2, 3, 4,
or
'\
-...
\...
K, L, M,
--------
N, -------
Methodolow
Delleloping the concept of structure of atoms through
c,la.tsr-oonztzctivity (Phuse 1 to 3)
A leader was selected from Std. IX and was
i
I
I
provided w ~ t ha card representing nucleus
*
0 I
The other students were provided with one card
each, representing an electron
0
?'he teacher writes the name of an element
(
llydrogen, Helium, Neon, etc.) on the blackboard.
I he leader of the team carrying the card of nucleus
takes his position at the centre. The members holding
tlie cards with electron has to form a circle
representing an electron in a
shell and finally the
students make the structure of the element written on
tlle blackboard.
I
Methodology
- - - - --
I)rcig~~rrrnnluticrepresetztation of the classroom activity
.sllo~citrg the s1r.lcc-lure ofntorns
Hydrogen
..............
....
.- K ~ht&'-..
b
(. ..@?
+.-....................
$g)$
Helium
+..................--.*..
..-..................-.
K Shell
J'\
xi-..-v'
Phase 3)
Neon
...
...................
....
...
*K Shell
I't.o~,rcic>oppot.tzrtllty to,fiizciout the capacity of electron shells
/
/
,-
,,A
Shell
2 electrons
/
I., Shell
~3
8 electrons
\
IZ1 Shell
a 18 electrons
IV Shell
032 electrons
I
-
Methodology
. ---
l:'t~cot~rccge
students to draw the structure of Hydrogen,
Helirinr, Litltiunt and Cltlorine and Argon
1 proton
1 electron
,,
1
1,
,
,
-.
~
'.
(1 electron)
Proton
Fig. 4.19 Hydrogen atom
- -
Methodology
-.-
Structure of Helium atom
2
11
K Shell (2 e)
-.
\
2 protons
2 electrons
\..
.&..
,__
,/
--+-*,'
,.-
Fig. 4.20
Helium atom
K Shell is the lowest level which
can accommodate upto 2 electrons
Structure of Lithium atom
-
3 electrons
<13>
.-O----.,.
0
\
KSheIi(2e)
\
"
,
'\\. . . -
-
L Shell ( 1 e )
/
.
/'
. ._---
/
Fig. 4.21 Lithium Atom
c = electron
Structure of Chlorine atom
Fig. 4.22 Chlorine atom
upto a maximum of - 8 electrons.
-
.-
Methodology
Structure of Argon atom
18 electrons
-
20 neutrons
K Shell (2 e)
L Shell(8 e)
,\
\
---.. --./
--- 9 3 . 2
'
-
r-i
\\
\..
. <;t-.---c
..
~~
Fig. 4.23
-
M Shell(8 e)
Argon atom
~-~-~ - - - ~ ~
I hll Shell is the third
-.
I1i;txlrnunl
of 18 electrons
~-
~
I!?I Shell
.
--~-.
can hold upto maximum of 32 electrons
-
Methodology
-.
Strucrur~ngmodel fbr representing the main constituents of atom
,---
,/
the atomic
centre
centre
\
Cluster together to form
(7
Nucleus
Together becomes
Electrons
mo\.lng round
very l'asr around
/
cl~llkl-e~r~
le\:els
/"
,"
,/'
~-./.
ATOM
=
w
ELECTRON SHELLS
Ilic 1111cleus
at
'\
(
K SHELL
L SHELL
G
M SHELL
c
N SHELL
Fig. 4.24 Structural representation of atom
Stlr~1r11t.s
rrr-e c>l~c,our-ageri
to calculate the maximum number of
elecft.oils tlzc~tcan he accommodated in each shell given in
(lirblc. 4 17)
Table 4.2 Maximum number of electrons that can be accommodated
in the shell
of
Shells
NO.
Shell
Maximum Number of Electrons
That can be accommodated
In the shell
Attention
-- -
~
~
~
I<lectron shells are imaginary circular paths of the
clectron.
I< Shcll can hold a maximum of 2 electrons.
I . Shell can hold a maximum of 8 electrons.
M Shcll can hold a maximum of 18 electrons.
N Shell can hold a maximum of 32 electrons.
n'" Shell can hold a maximum of 2n2 electrons.
- . - .- .--
,
'
,
Methodology
__ ---
/
Scientific Terms / Concepts
1
-CONCLUSION
The path of the electron around the
nucleus is called shell or orbit
,7-
A
I
1I
(
EVALUATION
I ) Define an electron shell
( 2 ) Fill in the blanks.
K shell can hold a maximum of
electrons.
(11) 1. shell can hold a maximum of
electrons
( l i l ) n"' shell can hold a maximum of
electrons
( 3 ) Match the following:
(I)
I
I
--
~
Number
of Electrons
-- -.
-.
~
8
1
(4) Draw the atomic structure of the following
I
atoms
( i ) Hydrogen (atomic number = 1)
(atomic number = 6)
( i i ) Carbon
(atomic number = 1 1 )
(iii) Sodium
i
i
I
ii
---
.
~
J
~~
297
UNIT 7
-
CHARACTERISTICS OF ELECTRON CLOUD
-
.
.
-
--
----Learning Point
llectron cloud is the part of an
poss~bilityof finding electrons
.
.
.
. -.
-J\,
>
PREVIOUS KNOWLEDGE
- ~~-~
/.(*I
I/
/lie stutler2ts discuss the special features of the
o l ~ ~ c ~c.lo~cd
~ i ~ oof'
r ~a11citorn
S ~ i l i t(11.c~ e ~ z c ~ u ~ a gto
e d represent pictorially the
c.lraruc~teri.stic.s
of rlectron cloud
Electron cloud is
a region in which
electrons are
found
Electrons in the electron cloud circle
very fast around the nucleus
Electron cloud is
the electrically
negative part of
( an
atom
(4)
Electrons circle at
dif'ferent levels in
the electron cloud
called
electron
1 shells or orbits
--
--
Methodology
- . -- -- -
-
Each orbit can hold
1" Orbit-2 Electrons
a definite number
2"dOrbit-8 Electrons
of electrons
3rdOrbit-18 Electrons and so on
Electron
(-loud I S the
lighter part
o l thc atom
-
--
4
-- -
-
-.
Methodology
Attention
-
--
Atoms are built up of protons, neutrons and
electrons
Protons and neutrons are present in the
nucleus
The electrons revolve in orbits around the
nucleus
-
-
\
.\-
ELECTRON CLOUD
1
.
&
CONCLUSION
Electron cloud is the part of an atom
in which there is possibility of finding
electrons
Answer the following questions:
( 1)
(
What do you mean by an electron cloud?
II
(2) Define an electron shell
/
(3) Give one word answer:
(i) Imaginary path through which
electrons revolve
1
(il)
Where do you see the electrons?
I
UNIT 8 RELATIVE MASS OF FUNDAMENTAL PARTICLES
Learning Points
(i) Protons and Neutrons have
a mass approximately one
( ~Electrons
i)
have a mass
111840 relative to the mass
of a Hydrogen atom
I
- -~
~-
PREVIOUS KNOWLEDGE
Rec,nlling the following concepts
Nucleus contains protons and neutrons
u
Electrons are present outside the nucleus
u Nucleus is the heavy part of an atom
u Mass of nucleus is the total mass of protons and
neutrons
Students are encouraged to draw the structure of
ltycfrogen atorn.
P~.o\~i(Ie
opportutzily to identih the relation between the mass
c?f HlrIrogen atom and the mass of a proton (discussion and
I
No. of electrons in a Hydrogen atom.
(1)
(11)
No of protons in a Hydrogen atom.
(1)
( 111)
No. of neutrons in a Hydrogen atom
(0)
(IV)
The massive particle in a Hydrogen atom(1 Proton)
\
\
'\
--
-
-
Methodology
.- -..-
Students are encouraged to prepare Table showing the mass of
fundarneiztalparticles with respect to the mass of hydrogen atom.
Table 4.3
Mass of fundamental particles with respect to mass of
I
Hydrogen atom
Proton
--
Mass
Nearly equals to the mass of
hydrogen atom
-
Neutron
Nearly equals to the mass of
hydrogen atom
1
Position
Nucleus
I
1
Nucleus
Outside
protons and neutrons
-
--
Nucleus
-
Students arc7 encouraged to prepare Table showing the
nppro.rimate selative mass of fundamental particles.
Table 4.4 Approximate relative mass of fundamental particles
I
I
7 0 HYDROGEN
1
Equal to Hydrogen
Atom
- 1
1
Proton
/Ieu6111
Electron
-
HYDROGEN ATOM)
-11.-
Equal to Hydrogen
1
i
compared to
Hydrogen Atom
-
-
(Mass of electron is
considered as Zero)
Provlde
opporturlity
to
compare
the
Diagrammatic
representutiot~sof masses ofproton, neutron and electron.
(
1
the masses of
and n
neutrontn)
Equal Mass for Proton and
Neutron
-\
C'oruparing
\
the masses of
a proton (p)
and a
I tydrogen ( H )
--
a
L7~
~
. ~ - - -
Equal Mass for Proton and
Hydrogen
masses o t a
proton ( p )and a
electron (e)
I
Mass of e ectron is very small
when compared to mass of
proton in an atom
-
Methodology
Protons and neutrons in atom have almost
equal mass.
'I'he mass of an electron is approximately zero.
/
'
I
Scientific Terms / Concepts
/'
1
MASS OF ELECTRON
MASS OF PROTON
--
Methodology
0
CONCLUSION
(1) Proton and Neutron have mass
approximately one
(2) Electron has zero mass
EVALUATION
(I)
What is the relative mass of proton?
I
( 2 ) What is the relative mass of neutron?
(
( 3 ) What is the relative mass of electron?
( 4 ) Name 2 fundamental particles having
I1
I
-
--
-
-- -
-
.
--
Methodology
UNIT 9 ATOMIC NUMBER
Learning Point
Atomic number of an element
IS
the number of protons in
cach atom or the number of
electrons 1r1 a neutral atom.
-
PREVIOUS KNOWLEDGE
C
1'1.or~~d~rig
opportunzty to recall the following concepts:
J
U~fferentatoms have different number of protons
J
An atom has equal number of protons and electrons
A
An atom possesses mass which is due to the presence
of nucleus.
~~
_ _
.
DEVELOPING THE CONCEPT OF ATOMIC
(I )
Methodology
NUMBER
Erzcourage students to draw the structure of Oxygen
c~torll
(Atomic number of Oxygen 3 8 )
Fig. 4.25 Structure of Oxygen atom
Methodology
(2) ltientlfi~ngthe rzumber of protons and electrons in an
o.y\gerz
trtoril
(zf atomic number is given)
Students are encouraged to calculate the number of protons and
electrons in an Oxygen atom to identify the relation between the
number of protons, number of electrons and atomic number.
.-
-
-- -.
Number of Protons
=8
Number of' electrons
= 8
Atomic number
= 8 (Given)
Nutnber of: Protons
=
Atomic Number
Number of Electrons
=
Number of Protons
Atomic Number
=
Number of Electrons
(A~omicNumber
=
Number of Electrons in a
Neutral Atom)
-
-
-
.
-
-
Methodology
---
Stude11t.r are directed to establish the relationship between
otorrllc number, number c?fprotons and number of electrons
Ji-orr~7irhle 4.5
Table 4.5 Atomic number, number of protons and number of
electrons of elements
Hydrogen
-~
--
~
Helium
<:arbon
2
2
2
6
6
6
8
8
8
11
11
11
17
17
17
--
Oxygen
-
~
Sodium
- .
('hlorine
--
-
--.-
Atomic Number
= Number
of Protons =
Number of Electrons
(~t&&ke&to&ofebina~datcpn)
.
-
-
-. ---.
Methodology
Attention
In an atom electrons and protons are equal in
number.
'I'he number of electrons or protons are
referred to as atomic number
i
,/
~ - ~ ; i e n t i f Terms
ic
/ Concepts
--.-
ID
CONCLUSION
1 I--
Atomic number is the number of
protons in an atom or number of electrons
in a neutral atom
EVALUATION
1
I
I
(1 ) Define atomic number
(2) What is the relation between the atomic
number and number of electrons?
(3 ) What is the number of protons and
electrons in an atom with atomic number
17'?
(4) What is the atomic number of an atom
containing 10 protons?
1
I
-
--
-
-
Methodology
--
UNIT 10
MASS NUMBER
Learning Point
Mass number of an element is
the total number of protons
and neutrons present in an
1
I
atom.
-- -
PREVIOUS KNO
--
Proviciing
opportunity
to recall
the following
concepts
o Nucleus is the massive part of the atom
u
Protons and neutrons are the massive particles and are
present inside the nucleus
u
Every atom has mass.
-
- -
-
Methodology
- ----
DEVELOPING THE CONCEPT OF MASS NUMBER
Encourage students to represent the structure of
CARBON, OXYGEN And SODIUM A TOMS
Fig. 4.26 Structure of Carbon atom
Provide opporturzity to calculate the mass number of Carbon
~-
\
Number of protons
=
6
Number of Neutrons
=
6
Total Number of massive particles
=
6+6=12
'l'herefore MASS NUMBER
=
12
\
J
--
-
Methodology
--
Fig. 4.27 Structure of Oxygen atom
Provide opportunity to calculate the mass number of Oxygen
atorll
f
Number of protons
= 8
Number of Neutrons
= 8
Total Number of massive particles = 8 + 8 = 16
Therefore MASS NUMBER
=
16
\
~~
Methodology
~.
Figure 4.28 Structure of Sodium atom
Provide opporturzity to calculate the mass number of Sodium
aton1
/
,
Number of protons
=
11
Number of Neutrons
=
12
'Total Number of masslve particles
=
1I
'Therefore MASS NUMBER
=
23
+ 12 = 23
Ider~tlj~zngthe relation between mass number, number of
protor~srlrzd number of neutrons.
-
-
-
-
Methodology
-
11( ACTIVITY
(
Students are encouraged to recall the number ofprotons
and neutrons in the Hydrogen atom and calculate the mass
number.
/
Number of Protons
I
=
I
1
Number of Neutrons = 0
Mass Number
-
---
--
=
Number of Protons +
Number of Neutrons
=
-
1
+
0
=
1
--
-
-
-
A
-
Methodology
Providing opportunity to find out the atomic number,
Mass number. No. of electrons, no. of protons, and no. of
neutrons using the Table
Table 4.6
Number of electrons, protons, atomlc number and mass
number of elements
Using Table 4.6 students write the number of electrons,
protons, neutrons, atomic number and mass number of Hydrogen,
Helium, Carbon, Oxygen, Sodium, Chlorine, Nitrogen, Neon,
Magneslum and Sulphur
-.
-
-
--
Methodology
-
Developing the equation showing the relation between number
of neutrons, mass number and atomic number
Number of neutrons = Mass number - Atomic number
C/Ib))Attention
Mass Number is equal to the total
number of protons and neutrons
//
,
Scientific Terms / Concepts
L..
MASSNUMBER
l
_
--2_-
I
/
Mass number of an element is the total
number of protons and neutrons present in
I
Methodolorn
(d.
EVALUATION
/
I
I. Answer thefollowing
(1)
Define mass number?
( 2 ) The mass number of A1 is 27 and
atomic number is 13. Find out the
number of protons, electrons and
neutrons present in it?
11. Exurnine the table given below andfind out
the
missing numbers (proton /electron/
ileutron/atonzic number/mass number)
Element
Beryllium
Mazesiurn
I
I
Number of
'Iectons trons trons
Atomic
Mass
Number
Number
---
23
-
Sodium-.
---
-----
-----
-
-
UNIT 11
--
Methodology
- .--
REPRESENTATION OF AN ATOM
Learning Point
All atoms can be represented
by uslng mass numbers and
atomic numbers
Providing opportunities to recall the following concepts
J
Symbols are short hand representations of atoms
u
Symbol represents an atom of the element
Familiarizing the symbolic representation of atoms
l?rample I]
-
-up7
\
/
Symbol for Hydrogen atom
1
1
1
Atomic number of Hydrogen
Mass number of Hydrogen
+1 1
I
/
~
~
~~
Methodology
Provide opportunity to represent the short hand notation qf
Hydrogen atom
Providing opportunity to complete the Table 4.7 showing
the relation between atomic number, mass number, no. of
electrons, no. ofprotons and no. of neutrons.
Table 4.7 Relation between atomic number, mass number, no. of
electrons, no. of protons and no. of neutrons
--
-
-
-
Methodology
--
-..
-
Students are encouraged to represent short hand notation of Neon,
Carbon and Oxygen atoms
/
/'
,/
Symbol for Neon
/
i
Atomlc Number
Mass Number
--
a
--
'\-. i
\
\
\
'\
+ Ne
10
~~
~~
Methodology
Methodology
Representing the short hand notation of an element
Mass Number
Mass Number
I
SYMBOL
SYMBOL
Atomic Number
Atomic Number
0
CONCLUSION
Atoms are represented symbolically
using symbol, atomic number and mass
I
J
1
2
-
EVALUATION
I At~swerthe following:
( 1)
I
1
d
I
Find out the number of protons,
neutrons and electrons present in the
atoms given below.
Carbon, Nitrogen, Sodium
( 2 ) Draw the models of the above atoms.
(3) Write down the short hand form of the
following atoms.
1
I
(a) Oxygen
(c) Boron
(b) Calcium
(d) Copper
I
-
Methodology
-
-
-
( 1)
Draw the structure of the following atoms
showing the nucleus containing protons and
1
neutrons and the orbits with the respective
electrons.
( i ) Lithium
( i i ) Aluminium
(iii) Silicon
( i v ) Calcium
(2) Prepare
an
album
including
the
major
contributions of J.J. Thomson, Rutherford and
James Chadwick.
(3) Prepare a radio talk on the discovery and
1
-.- ..
properties of electrons, protons and neutrons.
--
-
--
-
-
-
--
Methodology
TEST YOUR KNOWLEDGE
(1)
Name the following:
(i)
the basic unit of matter
(ii)
the sub-atomic particle with positive charge
and unit mass
(iii) sub-atomic particle with no charge and unit
mass
(iv) the shell that can hold a maximum of 18
electrons
(iv) the scientist who discovered electrons
(v)
(2)
the particles present inside the nucleus
Define the following:
(i)
nucleus
(ii) Nucleons
( i i i ) Atomic number
(iv) Mass number
(1)
(3)
electron shell
Name the scientists behind the discovery of electrons,
protons and neutrons.
(4)
Why is sodium atom electrically neutral?
(5)
Explain the parts of an atom
(6)
Draw the atomic structure of the following atoms:
(a) Lithium (b) Neon
(7)
(c) Sodium
What is the relationship between atomic number and
mass number?
(8)
Write down the number of protons, neutrons and
electrons present in:
( i ) Chlorine atom(Atomic number = 17, Mass number
=
35) and
(ii) Calcium atom)Atomic number = 20, Mass number = 40)
(9)
Develop models of the nucleus for the following atoms:
(a) Helium
( 10)
(b) Chlorine
Explain the charge and mass of fundamental particles in
an atom.
(1)
L. R.Daniel, R. G. Scott and E. M. Edward (1993). Chemistry-
Principle and Practice. USA: Saunders College Publishing.
(2)
R. M.Gallagher and P. Ingram. (1994). Chemistry. Oxford: Oxford
University Press
(3)
R. M.Gallagher and P. Ingram. (1996). Chemistry made clear.
Oxfbrd: Oxford University Press
(4)
U. Garvie. R. John and A.Robertson (1993).
Core Chemistry.
Oxford: Oxford University Press.
(5) B. Harrow (1927). Eminent Chemists of Our Time. Van Nostrand,
New York
((I)
C;. Jones, M Jones and D. Acaster (1993) Chemistry. Cambridge:
Cambridge University Press
(7)
C'.N.R. Rao
(1999)
Understanding
Chemistry. Hyderabad:
llniversities Press (India) Ltd.
(8)
M.H. Robert and James T. (1997). Science matters. Hyderabad:
Universities Press (India) Ltd.
(9)
C;. R. Tracy., H.E. Tropp and A.E Fried1 (1974), Chemistry. Holt,
Rinehart and Winston. Inc.
-
-
-
-
Methodology
--
ACHIEVEMENT TEST IN CHEMISTRY
( SECONDARY LEVEL )
Time: 1 hour
Max. Marks: 25
Instructions: Answer all the questions
(A) Choose the correct answer from the bracket.
(1) Electron was discovered by
(a) J.J. Thornson
(b) Chadwick
(c) Rutherford
(d) John Dalton
(2) 'l'he central part of the atom is called
( a ) Electron
(b) proton
( c ) Neutron
(d) nucleus
( 3 ) 'fhe maxlmum number of electrons that can be accommodated
In the second shell is
(a) 2
(cl
18
(b) 8
id) 32
(4) I'he sub-atom~cparticle with a positive charge and unit
'S
- -
( a ) electron
(c)
neutron
(b) proton
(d) positron
mass
(5) The shell nearest to the nucleus is
(a) K
(b) L
(c) M
(d)
N
(6) Atom~cnumber of Phosphorous is 15; its number of electrons
in the atom will be
(a1
2
(b) 8
(c,
10
(4 15
(7) The particles which are equal in number in an atom are ( a ) proton & neutron
(c )
proton & electron
(b) neutron & electron
(d) nucleus & proton
(8) 'file neutral particle in an atom is
(9)
( a ) electron
(b) proton
( c neutron
(d) nucleus
1 he mass number of magnesium is 24 and has 12 electrons.
'I he number of neutrons will be
(;I)
II
(b) 12
(c,
21
(dl 23
(10) Uas~c:fundamental unit of matter is ( a ) molecule
(c 1
atom
(b) element
(d) ion
( 1 x 10 = 10 marks )
-
--
-
--
--
Methodology
(B) Define the following:
( a ) Electron shell
( b ) Mass number
(c) Nucleons
( 2 x 3 = 6 marks )
(C) Explain why atom as a whole is neutral with a suitable
example.
( 4 x 1 = 4 marks )
(I))
Draw the structure of the following atoms showing the
nucleus containing protons and neutrons and the orbits with
the respective electrons.
( a ) Nitrogen (Atomic number = 7, Mass number = 14)
( b ) Silicon (Atomic number = 14, Mass number = 28)
(2,12x 2 = 5 marks )
( I l l ) ACHIEVEMENT TEST I N CHEMISTRY
The Investigator prepared an Achievement test in Chemistry
for Educationally Backward students
studying in Standard IX
based on the topics selected for the preparation of Remedial
Teach~ngMaterials
74 test items were included in the draft test.
multiple choice questions are included in Section A
Twenty
(one mark
allotted for each item). In Section B there are ten questions and
students have to answer in a word or in a sentence; one mark
allotted for each question.
Section C consisted of six short
answer and one short essay type questions.
Separate answer
sheets were provided to students.
ltem Analysis
ltem analysis is concerned primarily with two characteristics
of items namely item difficulty and item discriminating power. Item
analysis
IS
done to find out the suitability of the test item. Any
test can be improved through selection, substitution o r
revision of items.
The total scores obtained for each
candidate was calculated b y summating the scores o f the
individual items. The 300 response sheets were arranged in
the descending order of the total scores. The top 27 per cent
and bottom 27 per cent were used for item analysis.
--
.-
-
Methodology
~
The scores for each item in
both groups were used for
calculating the Discriminating Power (DP) and Difficulty Index(D1)
of each item. Items with Difficulty Index (Dl) between 0.37 to 0.6
and Discriminating Power (DP) above 0.4 were selected for the
final test. The selected items were printed i n booklet form with all
necessary instructions.
A sample of the final test is given in
Appendix 11. (The Achievement test was prepared on the basis of
the Blue print)
Validity & Reliability of the Tests
The procedure adopted for the construction of the final test
provides complete evidence for the validity of the test.
Face
validity of the test was ascertained by subjecting the test to
assessment by experts, for their comments.
The content validity of the test has been ensured through
the choice of items and the test construction procedures.
The
reliability of the test was found out using Split-half Method. The
Correlation test scores for the two halves was found out using the
Pearson's Product Moment Coefficient of Correlation.
The
reliability of the half test was 0.72. It was corrected by SpearmanBrown Prophecy Formula.
The
coefficient obtained was 0.84.
which shows that the test is highly reliable for the purpose.
SCORING K E Y OF ACHIEVEMENT TEST
Scoring key is given in Appendix Ill
VA1,IDATION O F REMEDIAL PROGRAMME DEVELOPED
The suitability of Remedial Teaching Materials in Chemistry
prepared
for
Educationally
Backward
students
studying
in
Standard IX was assessed by submitting the Remedial Materials
to experts in the field of Chemistry.
suggestlons
made
by
them,
In the light of the valid
appropriate
modifications
and
corrections were made in the Remedial Materials prepared. The
responses in the schedule were then subjected to statistical
analysis. The details of the Evaluation Schedule are presented in
the Analys~sPart (Chapter V). The list of experts are given as
Appendix I V .
(IV)
I
N
SCALE
FOR
EXPERTS
AND
SECONDARY
S('11001. CI-IEMISTRY TEACHERS
A rating scale was prepared by the investigator to collect
details regarding Remedial Instructional Materials on the following
aspects.
(I)
Suitability of the Remedial Instructional Materials
(11)
Availability of the resources
(111)
Practicability
The respondents were asked to go through the concepts
given in the rating scale and indicate their opinion by putting a
Cross mark(>() in any one of the three columns, viz., Great
Extent(GE), Some Extent(SE) and Not at AII(NA) [Appendix-Vj
(V)
QUESTlONNAIRE FOR EXPERTS AND TEACHERS (AT
SECONDARY SCHOOI, LEVEL)
(1)
Questionnaire for Experts
A questionnaire covering three major aspects was prepared
to collect the responses of Experts regarding the following
dimensions:
(i)
Necessity of Remedial teaching
(ii)
Need for
special training for
Secondary school
Chemistry teachers in Diagnostic testing
(iii)
Need for
special training
for
Secondary
school
Chemistry teachers in Remedial Teaching [Appendix
vr]
(2)
Questionnaire for Teachers
A questionnaire covering six major aspects was prepared to
collect
the
responses
of
the
Secondary
Teachers regarding the following dimensions:
school
Chemistry
~
(i)
-~ .
~~
Methodology
~p
Necessity of Diagnostic testing and Remedial Teaching
( ~ i ) Need for special
Chemistry
training for Secondary school
teachers
in
Diagnostic
testing
and
Remedial Teaching
( ~ i i ) Extent of Practice (Diagnostic testing and Remedial
teach~ng)
(IV)
Procedures
adopted
in
Diagnostic
testing
and
Remedial teaching
(v)
Practical difficulties
teachers while
likely to be encountered by
practicing
Diagnostic testing and
Remedial teaching
(VI)
The suggestions of Secondary School teachers for
the effective use of Diagnostic testing and Remedial
teach~ng in Chemistry at Secondary
School Level
[Appendix VII].
(VI) (;ENERAL D A T A SHEET
A general data sheet was prepared and administered along
with the other schedules to collect personal details about the
students like sex, locality of school, medium of instruction.
management of school, income and educational status of parents
(Appendix VIII).
-
-.
-
Methodology
.-
4.1.2 S A M P L E SELECTED FOR THE STUDY
The deta~lsregarding the sample selected for the study are
given below:
(i)
The investigator
selected 620 Educationally
Backward
students [based on the annual examination achievement
test scores of all school subjects in Standard VIII, First unit
test and first terminal (Examination) achievement test
scores of the same students in Standard IX] studying in
standard 1X of different schools in Kollam district. (On the
basis of Achievement tests students scoring less than 30%
for all school subjects selected as Educationally Backward
students).
(ii)
From the
620
Educationally
Backward
students
300
students scoring less than 30% in Chemistry were selected
for experimental study (The details are given in Table 4.8).
W h ~ l eselecting the sample, care was taken to give due
representation to variables like sex, locality, management,
community, income and educational status.
Table 4.8
SI.
-
The Sample selected for Experimental Teaching
Yame of Schools
I
-
--
-
11
Sex
Male
7
3.
I
4.
5.
6.
7.
I
Locality
Management
i
Govt. I Pvt.
Female I Urban
1 3 1
Rural
Medium of
Instruction
Eng i Mal
Govt. Girls H.S.
Chavara
20
St. Joseph G.H.S.
Neendakara
10
20
Govt. Girls H.S,
Vallikkeezhu
14
23
14
23
Vimala Hridaya GHSS,
Kollam
20
20
20
20
20
20
20
10
15
30
15
30
15
15
St. Aloysius HSS,
Kollam
15
30
10
20
10
20
TOTAL
Note: RT -Remedial Teaching LM - Lecture Method
SL - Self Learning
14
23
Educational
Status
High I Low
20
6
20
4
16
' 20
9
11
10
20
4
6
6
14
14
4
10
23
10
15
16
15
15
14
23
I
i
Type of
Teaching
Total
I
'
LM
20
SL
20
5
4
SL
20
16
LM
30
300
I
$
s
.
-
(iii)
-
--
- --.
-
Methodology
The Rating Scale was administered to 16 experts and
54
Secondary School Chemistry Teachers.
(iv)
A questionnaire was administered to 16 Experts and
54
teachers in Chemistry at Secondary School level
(v)
The general data sheet was administered to the 300
students selected for experimental study
4.1.3 EXPERIMENTAL DESlGN AND PROCEDURE
The basic experimental design adopted in the present
investigation was Pre- test Post- test parallel group design.
The ~nvestigatorselected 300 I X ' ~Standard Students from
seven Secondary Schools for the Experimental study. The topics
selected for experimental study were Periodic Table, Atomic
Strirctrrre urrd Oxidafiorr arrd Reduction. Care was taken to give
due representation to Sex,
Locality, Marragemerrt of Schools
,
Medirrnr ofirrstructio~rand Educational status of parents.
After selecting schools for the experimental study, the
investigator made necessary arrangements with the heads if the
schools selected for conducting experiments.
The investigator adopted three methods for teaching the
topics. The details are given below:
Remedial 'Teaching using Remedial Teaching Materials
Metllod I 1
Self learning Method using Remedial Teaching Materials
prepared
Method Ill
Lecture Method using textual materials
The details regarding the experimental procedure are given
below
I'KE-I ES'I
4.1.3.1
After
selecting
the
schools
for
experimental
invest~gatormade necessary arrangements with the
schools
for
conducting
experiments.
The
study
heads of
investigator
admlnlstered the Achievement test in Chemistry(Pre-test) to the
Treatment Groups Remedial Teaching Group-RT(N=100), Self
Learn~ng Group-SL(N=100)
and
Lecture
Method
Group-
LM(N=100) to assess the entry behaviour of the Educationally
Backward Students in Chemistry.
4.1.3.2
I-XPOSURE T O REMEDIAL TEACHING
The Group I (Remedial Teaching Group
Remedial teaching
-
RT) was exposed to
by the investigator, using the Remedial
Teaching Materials in Chemistry prepared by the investigator.
Facilities were provided to students to follow the procedures and
learning situations given in Remedial Teaching Materials The
previous knowledge of
the students was assessed
by suitable
activities and learning situations. Students were encouraged to
develop terms, concepts and principles through discussion,
observations, experiments, activities and projects.
4.1.3.7
FXPOSIJRE TO SELF-LEARNING
The Group II (Self Learning Group -SL) was exposed to
self
learning
materials after assessing the entry
behaviour
(Remedial Teaching Materials, prepared by the investigator for
Remedial
teaching
Group,
with
necessary
direction
and
modification was used as self learning material)
4.1.3.4
E X P O S U R E TO LECTURE METHOD
T h e Group 111 (Lecture Method Group-LM) was exposed
to Lecture Method using the textual material. The experimental
topics were taught by the investigator systematically with the help
of illustrations and audio v~sualaids such as charts , models and
experiments At the end of each class, follow up activities were
also glven
4.1.3.5.1 Immediate Post-test
The
investigator
administered
the
Achievement
test
in
Chemistry to the students in the Treatment Groups (RT, SL and
LM) immediately after the experimental teaching to assess the
terminal behaviour. (Same Achievement Test was used as Pretest and Immediate F'ost-test)
4.1.3.5.2
Delayed Memory Achievement
The Achievement test in Chemistry was administered to
the students ot the Experrmental Groups after three months to
assess
the
Delayed
memory
achievement.
(The
same
Achievement test in Chemistry was used as pre-test and delayed
Memory Achievement test)
General
Data
sheet
were
also
administered
experimental Group along with Immediate Post-test .
to
the
--
4.1.4
-
-
--
Methodology
-
S'I'ATIS'TlCAL TECHNlQUES
The
statistical
techniques
ernployed/adopted
in the
present study are listed below:
(1)
Analysis of variance and analysis of co variance were used
to study whether there is any significant difference among
the Treatment Groups (RT, SL and LM) with regard to
achievement in Chemistry
(2)
Test of significance of difference between percentages.
Methodology
-
-
REFERENCES
(1)
P . Tamir.(l971). An alternative approaclt to tlre corrstruction of
t~ritltiple clroice test item, Journal
of Biological Education.
v01.5,pp.305-307.
(2)
K.G.Tobion and W. Capie (1981 ). The development and validation
o f a groicp test of logical thinking. Educational and Psychological
Measurement Vol. 11,pp.413-424
(3)
D.F.Treagust(1986). Evaluating students' misconceptions by means
of'
diagriostic
multiple-clroice
items,
Research
in
Science
Education. Vol. 16, pp. 199-207.
(4)
A.J. Lien. (1971). Measurement arrd Evaluation in Learning.
Lowa:William C. Brown company.
(5)
J. K. Gilbert. (1977). The study of studerrt misutrderstarrdings irr
tlre pl~ysical scierrces,
pp.165-I71
Research in Science Education. Vo1.7,
