Download The Building Block of matter What is an atom?

Atom-Building blocks of matter
What are the main
All matter is composed of extremely small
particles called atoms.
•
Atoms of the given element are identical in size, mass and
other properties
• Atoms can not be subdivided, created or destroyed.
• Atoms of different elements combine in simple whole
number ratio.
• In chemical reactions, atoms are combines, separated or
rearranged
How does Dalton’s atomic theory support law of
conservation of mass during chemical changes?
How do these chemical changes between carbon © and
oxygen =(O) atoms account for law of conservation mass?
• C
+
OO
OCO
• 1 ‘C’ + 2 ‘O’ atoms
= 1 C + 2 ‘O’ atom
•
• C
+
O
CO
• 1C
+ 1 ‘O’ =
1 C + 1 ‘O’ atom
• # of atoms are same before and after chemical change. It is
according to Dalton’s atomic theory
How does modern atomic theory differ from
Dalton’s atomic theory?
Dalton’s atomic theory
• Atoms are indivisible
• Atoms of the same
Element are identical
• Atoms can not be
Destroyed or created
Modern atomic theory
Atoms are divisible
Atoms of the same element
May be different (Isotopes)
Atoms can be destroyed
(Nuclear reaction) E = mc2
JJ Thomson
JJ Thomson Discovered electron is an essential
particle of an atom in his cathode ray tube
experiment. He suggested electron pudding model
Draw JJ Thomson’s electron pudding model of atom and make your
decision and support if atom will be negatively charge, neutral or
positively charge particle?
Cathode rays made with negatively charged
particles
Thomson suggested for positive charge to
make electrically neutral atom
What was the idea that lead to discovery of
nucleus?
• According to Rutherford’s gold foil experiment,
draw the two parts of an atom and suggest why
atom is a neutral particle?
What three subatomic particles of Atom their
properties and their locations in an atom?
• Name
Symbol Charge Mass Location
• Protons
p
+1
1
In side nucleus
• Electrons e
-1
0 out side nucleus
• Neutrons n
0
1 In side nucleus
• Why an atom is neutral? # p = # e
• # positive charge = # negative charges
Counting # subatomic particles
• What is atomic Number? # protons in the nucleus is called atomic #
• What is the importance of atomic number of an atom of an element?
• The Atomic # determines the identity of an element ( Atomic # =11, it
is sodium element)
• What is mass Number of an atom?
• Sum of # protons and # neutrons is called mass number (nucleons).
• How will you calculate # neutrons in an atom if its atomic number and
mass number are given?
• Mass number – atomic number = number of neutrons
Nuclear atom
a) What are isotopes of an element?
b) What are three isotopic symbols hydrogen atoms of
protium (H), deuterium(D) and tritium(T)?
C) How they are similar and different from each other?
Symbol
• Protium
• Deutrium
• Tritium
1 H
1
Mass #
1
2 H
1
3 H
1
1
2
3
Atomic number
#P
#e
1
#n
1
0
1
1
1
1
1
1
1
2
Compare and contrast the two isotopes of
35
37
chlorine ( 17Cl and 17Cl)
35 Cl
17
Atomic #
#P
#e
#n
Mass #
17
17
17
18
35
37 Cl
17
17
17
17
20
37
Calculate All the # subatomic particles in the
following atom with hyphen notation
• Hyphen notation Symbol Atomic# mass # #p
235 U
• Uranium -235
92
235
92
92
238 U
• Uranium -238
92
12 C
• Carbon -12
6
12
6
6
13 C
• Carbon -13
6
63 Cu
• Copper -63
29
65 Cu
• Copper -65
29
#e
#n
92 143
6
6
• Atom has two parts. At the center, there is ______1____charge due
to____2_____ which have ____3______ charge. Intense mass at
center is due to ____4_______ and _____5____ which are neutral.
_____6__ and ___7______ have the same __8______. Negatively
charged particles are called ___9_______ and these are located at
out side ___10______. Atom has no charge because of # ___11___
___12____ = #__ 13 _____Subatomic particles nucleus are
collectively called _____14_____. # neutrons = ____15_____ ____16_______. An atom has #p = 54, # n = 77, The name of the
element is ___17_____ and it has ___18_______ electrons. It is
neutral atom because of ___19_____ number of _____20___ and
____21_______.
Average atomic mass
• There are 2 Type of marbles A and B. 30 marbles of A type have
mass of 37gram each, and 70 marbles of B type marble have
mass of 35 grams each. What is their average atomic mass
• What are their relative abundances?
• Relative abundance of A =
Relative abundance of B =
# of A marbles x mass A
+ #of B marble x mass B
• Average atomic mass = _________________________________
Total number of marbles
Does the average mass be closer to mass of A or mass of B
marbles?
Carbon -12 is a standard atom
• What is 1 atomic mass unit(amu)?
• 1C =
? Amu
1amu =
• Average atomic mass = The average atomic mass of an
element is the weighted average mass of isotopes of
that element.
• Two isotopes of chlorine 3517Cl and 3717Cl have
% abundance of 70% and 30% respectively. What is its
average atomic mass? It is closer to isotopes ---- Why?
1) 99.9885 % atoms of hydrogen -1 has mass 1amu, and .0115%
atoms of hydrogen -2 has mass 2amu. What is its average
atomic mass?
2) 98.93% carbon -12 has mass = 12 amu, and 1.07 % carbon
has mass = 13 amu. Calculate average atomic mass
• 3) There are three isotopes of oxygen. 99.757% Oxygen-16
has mass of 15.994 amu, 1.07% oxygen-17 has mass of
16.999123 amu, and 0.205% oxygen has mass of 17.99916
amu. Calculate average atomic mass of oxygen.
• 4) 69.15% copper-63 has mass =62.9296 amu, whereas
30.85% copper -65 gas mass = 64.92779 amu. What is its
Average atomic mass? Is the average atomic mass be closer
to Cu-63, or Cu-65?