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Science 2nd prep 1st term 1st lesson
Many attempts are made by scientists for classification of elements to be easily studied
Attempts to categorize the elements
* The periodic table of Mendeleev
* Periodic Table of Moseley
* the modern periodic table
The periodic table of Mendeleev
it is the first read periodic table.
Mendleev prepared 67 cards to represent the elements.
He arranged them according to its atomic weight.
He arranged the elelments in vertical columns ( groups )
He discovered that atomic weight increase by moving from left to right
In period row.
1 - He clarified a relationship between
elements and their properties.
2 - he left spaces (empty cells) in his
table and predicted the discovery of
new elements.
1– He had to deal with the isotopes
of one element due to the difference
in their atomic weight.
2- He had to make a disturbance in
the ascending order of atomic
weights for some elements,to put
them in a groups.
3- he corrected the wrong estimated
atomic weights of some elements.
Why did he put more than an element in one place???
The periodic table of the Moseley
In 1913, Rutherford discovered that the nucleus of atom contains positively charged
Science 2nd prep 1st term 1st lesson
- He arranged elements in an ascending order according to their atomic numbers.
- he added the inert gases in the (0) zero group.
- He classified the elements of each group into two subgroups (A&B) as they differ in their
- he allocated a place below his periodic table for the two groups lanthanides and actinids.
The modern periodic table
After the Danish Scientist Bohr discovered the main energy levels. And their sublevels, the
Elements were classified in modern periodic table according to:
-Their atomic numbers
- The way of filling the energy sublevels with electrons.
Each main energy level contains a number of energy sub-levels
equal to its number
*For example the main fourth energy level N consists of four
energy sub-levels which
Science 2nd prep 1st term 1st lesson
Science 2nd prep 1st term 1st lesson
Description of the periodic table
*The number of known elements until now are 116 elements, 92 elements are available in
the earth’s crust, the rest of the elements are prepared artificially.
*Elements of (A) groups lie on the left and right of the table, you can locate their position
in the modern periodic table by knowing their atomic numbers and vice versa.
*The elements of (B) groups lie in the middle of the table.
*Recently discovered elements are not found in nature but they are prepared artificially.
These elements are radioactive elements, their nuclei are decayed in less than a second.
*The modern periodic table is consists of:
7 horizontl periods.
16 vertical groups (18 vertical columns )
* the periodic table is divided into 4 main blocks
S block
Two sets are
denoted by the
symbol A
Left side of
periodic table
d block
10 groups
symbolized by the
symbol B is called
Located in the
middle of the
periodic table
P block
consisting of 6
sets are denoted
by the symbol A
Except the zero
group (inert gas)
Located in the
right side of the
periodic table.
F block
is composed of two
Lanthanidat and
Located below the
periodic table.
Locate any element in the periodic modern table
(A) the atomic number of the element: we are distributing the electrons on the energy
(B) number of energy level determine the period number.
(C) number of the outer most shell energy level determine the group number.
Exercise 1
An element lies in group (3B) and period (4). Mention its kind and in which block it lies?
- it is transitional element. And lies in : d block
Science 2nd prep 1st term 1st lesson
Periodic table
Inert gases
‫الجدول الدوري‬
‫االشعة السينيه‬
‫الغازات الخاملة‬
‫مدرات فرعيه‬
Atomic weight‫الوزن الذري‬
‫نظائر مشعة‬
‫مجموعات فرعيه‬
Exercise 2
Locate the position of each of the following??
1- hydrogen 1 H
2- Neon 10 N
3- Phosphorous 15 P
4- Calcium 20 Ca
Exercise 3
Calculate the atomic number of each of the following elements:
1- element (X) exists in the second period and in group (7A).
2- element (Y) exists in the third period and in group zero.
Complete the following statements:
Mandeleev arranged the elements according to -------------------Moseley arranged the elements according to -------------------The scientist ------------ discover the atom main energy levels.
In modern periodic table,elements arranged according to -----------and ---------Elements of S-block located in the -------------------of the table.
The d-block contains -------------elements.
Zero group represent ---------gases.
The ---------- of an element equals the sum of numbers of electrons which rotate
around the nucleus of its atom
Choose the correct answer:
1 – Mosely classified the elements of each group into ………………sub-groups.
a. 2
b. 3
c. 4
d. 5
2 – the nucleuw of the atom contains………………………
a. positive electrons.
B. negative electrons
c. negative protons.
D.postive protons.
3 – the scientist who discovered that the nucleus of atom contains positively charged proton is ……
a. Bohr.
c. Rutherford
d. Moseley.
Science 2nd prep 1st term 1st lesson
4 – the number of known elements in the modern periodic table till now is ……………………………
a. 216
b. 116
c. 316
d. 16
5 – the modern periodic table consists of ………. Vertical groups.
a. 7
b. 10
c. 14
d. 16
6 – the modern periodic table consists of ………………… horizontal periods.
a. 7
b. 10
c. 14
d. 16
7 – the elements which occupy the middle block (d) in the periodic table are called ………….. Elements.
a. transition
b. alklali
c. alkaline earth
d. noble.
8 – the block which contains the groups (1A) and (2A) in the periodic table is ……………………
a. s
b. p
c. d
d. f
9 – if the atomic number of an element is 15, so its group is located in ………….. Block.
a. d
b. s
c. f
d. p
10 – Lanthanides and actinides are located in the located in the ……………block.
a. s
b. f
c. p
d. d
11 – Elements of group (6A) in the periodic table have the same ………………..
a. number of protons.
B. number of energy levels.
C. number of neutrons.
D. number of electrons in the outer levels.
12 – in the periodic table , the elements which are identical in properties lie in the same ……………..
a. period.
B. group
c. nucleus.
D. energy level.
13 – the element 12X lies in ………………… in the periodic table.
a. period 2 and group 2 A
b. period 2 and group 3A
c. period 3 and group 2A
d. period 3 and group 4 A
14 – the element which its atomic number is 17 is similar in its chemical construction to the element
which its atomic number is ………………….
a. 2
b. 7
c. 9
d. 19
My wishes,