1. The document discusses the structure of atoms, including the development of atomic models from Dalton to Chadwick. It describes the subatomic particles that make up atoms - protons, neutrons, and electrons - and how they are arranged. 2. Activities include identifying states of matter based on particle arrangement and movement, writing atomic representations, determining numbers of protons, neutrons and electrons, and describing isotopes and their uses. 3. Electrons fill specific electron shells around the nucleus, with the first shell holding up to 2 electrons and subsequent shells filling with increasing numbers of electrons up to a maximum. Valence electrons are in the outermost shell.

1. WAJA F4 Chemistry 2010 Chapter 2: The Structure of Atom
CHAPTER 2: THE STRUCTURE OF ATOM
A MATTER
Learning Outcomes
You should be able to:
describe the particulate nature of matter,
state the kinetic theory of matter,
define atoms, molecules and ions,
relate the change in the state of matter to the change in heat,
relate the change in heat to the change in kinetic energy of particles,
explain the inter-conversion of the states of matter in terms of kinetic theory of
matter.
Activity 1
Fill in the blanks with suitable word(s) in the box given
Ions tiny molecules discrete smallest take part
positively-charged in released atoms gas chemically
solid absorbed different arrangement movement liquid
1. Matter is made up of ………………………. and …………………… particles.
2. The tiny particles may be atoms ……………….. and ……………………….
3. An atom is the ………………… particle of an element that can …………………….. in a chemical
reaction.
4. A molecule is a group of two or more …………………… which are …………………… bonded
together.
5. An ion is a …………………………………. or negatively – charged particle
6. Diffusion occurs when particles of a substance move ……………… between the particles of
another substance.
7. Diffusion of matter occurs most rapidly in ………………… state, slower in ………………….. state
and slowest in …………………….. state. This is due to the different ……………………… and
………………………. of particles in the three states of matter.
8. Matter consists of small particles that always collide among each other. The particles move faster
when energy is …………………… and the particles move slower when the energy is
….………………..….
Activity 2
1. Complete the table below.
State of matter Solid Liquid Gas
Draw the
arrangement of
particles
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2. WAJA F4 Chemistry 2010 Chapter 2: The Structure of Atom
The particles are The particles are The particles are
packed …………….. packed ………………. …………….. apart from
Arrangement of
together in an together but not in each other and in
particles
………………………… ….……..………………. ……………………………
manner …………………………. motion.
Particles can only Particles can Particles can
Movement of …………………… and ………………………..., ………………………….,
particles ………………….. about ….……… and………… ……………………… and
their fixed positions throughout the liquid. ……………. freely
Attractive forces Particles are attracted Particles are held The attraction forces
between the by very …………….. together by strong between particles are
particles …………….. between forces but …………….. ……………….… forces
the partcles than the forces in solid
(moderately)
Energy content of
particles …………………….. ………………………. ……………………………
2. Underline the correct word in the passage below.
When heat energy is supplied to particles in matter, its kinetic energy (increases /decreases) and
the particles in matter vibrate ( faster/ slower). When matter loses heat energy, the kinetic energy
of the particles (increases/decreases) and they vibrate ( faster/ slower).
3. State the change of matter for each conversion in the spaces provided.
A …………………………… B …………….……………….. C……………..……………..
D……………………………. E …………………………….. F ……………………………
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3. WAJA F4 Chemistry 2010 Chapter 2: The Structure of Atom
4. Complete the passage below by using the words given below.
(solid, gas, boiling point, melting point, solid, gas, liquid, intermolecular, released, absorbed,
overcome )
The temperature at which a ………………………………… completely changes to a liquid is called
……………………………… Boiling point is the temperature at which a …………………… changes
into …………….. . During the boiling process, the temperature remains constant because the heat
energy is …………………… by the particles and is used to …………………...………………… the
…………………………… forces between particles.
5. The graph below shows the change in temperature with time when a matter in solid state was
heated.
O
Temperature/ C
D
B
C
A
Time/s
Based on the graph above, complete the table below.
Point States of matter Explanation in terms of energy change and movement of
particles
Heating causes the particles to ……………………….. more
A to B energy and vibrate ……………………….. The temperature of
the substance and the kinetic energy
…………………………………
Continuous heating does not cause the temperature of the
substance to increase. The energy absorbed is used to
B to C
…………………………… the forces of attraction between the
………………………. The constant temperature is called the
…………………..…………………………………………..
Continuous heating causes the temperature of the liquid to
C to D
…………………………… The particles move……………………
because their kinetic energy ………………………………………..
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4. WAJA F4 Chemistry 2010 Chapter 2: The Structure of Atom
6. (a) The graph below shows the change in temperature with time when a matter in liquid state is left
to cool.
Temperature / OC
P
Q
R B
Q A
A
A
S
D
Time/s
A
Based on the graph above, complete the table below.
Point State of matter Explanation
As cooling continues, particles lose their…………………………
P to Q
and move ………………………. . The temperature……………...
The stronger bonds ……………………. during freezing release
Q to R
energy. This energy released is the same as the energy
………………. to the surroundings during cooling. Thus the
temperature remains unchanged. This constant temperature is
called …………………………..
The ………………is cooled. The particles vibrate……………….
R to S
as the temperature ……………………….
(b) Complete the passage below by using the words given below.
(solid, gas, liquid, exactly balanced, decreased, increased)
Freezing point is the temperature at which a …………………… changes into ………………………
During the freezing process, the temperature remains unchanged because the heat lost to the
environment is …………………….….. by the heat released when the liquid particles rearrange
themselves to become solid.
B THE ATOMIC STRUCTURE
Learning Outcomes
You should be able to:
describe the development of atomic model,
state the main subatomic particles of an atom,
compare and contrast the relative mass and the relative charge of the protons, electrons and neutrons,
define proton number,
define nucleon number,
determine the proton number,
determine the nucleon number,
relate the proton number to the nucleon number,
relate the proton number to the type of element,
write the symbol of elements,
determine the number of neutrons, protons and electrons from the proton number and the nucleon
number and vice versa,
construct the atomic structure.
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5. WAJA F4 Chemistry 2010 Chapter 2: The Structure of Atom
Activity 3
1. Complete the table and draw the structure of each atomic model.
Model Structure Characteristic
Dalton’s atomic model
proposed by The atom was imagined as a small
indivisible ball similar to a very tiny ball.
……………………
in 1805
Thomson’s atomic
model proposed by J.J Thomson discovered ……………….., a
negatively-charged particle.
…………………….. The atom was described as a sphere of
in 1897 positive charge embedded with electrons.
Rutherford’s atomic
model proposed by Ernest Rutherford discovered …………….,
a positively-charged particle in an atom.
…………………… in The central region of atom has a very small
1911 positively-charged …………………..…,
which contains almost all the mass of the
atom.
Bohr’s atomic model
proposed by The electrons in an atom move in
………..……… around the nucleus which
……………………in contains protons.
1913
Chadwick proved the existence of
Chadwick’s atomic ……………….., the neutral particle in the
model nucleus.
proposed by The nucleus of the atom contains protons &
…………..…………. in neutrons, and the nucleus is surrounded by
1932 electrons.
Activity 4
Fill in the blanks and complete the table.
1. Atoms are made up of subatomic particles namely protons, …………… and …………..
2. ………………………and …………….. are found in the nucleus of an atom while electrons surround
the nucleus.
3.
Subatomic particle Symbol Relative mass Relative electric charge
Proton
Neutron
Electron
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6. WAJA F4 Chemistry 2010 Chapter 2: The Structure of Atom
4. The proton number of an element is the number of ………………… in its atom.
Proton Number, Z = Number Of Proton
5. Protons and neutrons are collectively called nucleons.
The nucleon number of an element is the total number of ………………….. and
……………….. in its atom.
Nucleon Number, A = Number Of Proton + Number Of Neutron
6. The nucleon number is also known as the ……………………………..
……………………… = Nucleon Number -- Proton Number
= A -- Z
7. The standard representation for an atom of any element shows the proton number and the
nucleon number of the element. It can be written as follows:
A
Z X
# A – Nucleon number
Z – proton number
X – symbol of element
1 21 Proton number 2
H Sc Nucleon number He
1 45 4
3 4 5 6 7 8 9 10
Li Be B C N O F Ne
7 9 11 12 14 16 19 20
11 12 13 14 15 16 17 18
Na Mg Al Si P S Cl Ar
23 24 27 28 31 32 35 40
19 20 21
K Ca Sc
39 40 45
By referring to part of the Periodic Table of Element above, complete the table below.
Proton No. of Nucleon No. of Standard
Element Symbol
number neutrons number electrons representation
Scandium
Aluminium
Argon
Beryllium
Boron
Calcium
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7. WAJA F4 Chemistry 2010 Chapter 2: The Structure of Atom
Carbon
Chlorine
Fluorine
Helium
Hydrogen
Lithium
Magnesium
Neon
Nitrogen
Oxygen
Phosphorus
Potassium
C ISOTOPES AND THEIR IMPORTANCE
Learning Outcomes
You should be able to:
state the meaning of isotope,
list examples of elements with isotopes,
determine the number of subatomic particles of isotopes,
justify the uses of isotope in daily life.
Activity 5
Fill in the blanks.
1. Isotopes are atoms of the same element with the ………………………. of proton but
……………………………….. of neutron.
2. Complete the table below:
Number of Symbol of Number of Number of Number of Name of
Element
isotopes isotopes protons electrons neutrons isotope
1
1 H 1
1 Hydrogen-2
Hydrogen 3
1 2
16
8 O 8 8 Oxygen-16
8 9
Oxygen 3
18
8 O
6 Carbon-12
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8. WAJA F4 Chemistry 2010 Chapter 2: The Structure of Atom
Carbon 3 6 7
14
6 C 6 8
35
17 Cl 17
Chlorine 2
17 20
35 Bromine-80
Bromine 2
35 35 Bromine-81
3. For each of the isotope list below, state one of its uses.
a) Gamma rays of Cobalt-60: ………………………………………………………………….
b). Carbon-14: …………………………………………………………………………………..
c). Phosphorus-32: ……………………………………………………………………………..
d). Sodium- 24: …………………………………………………………………………………
e). Iodine -131: ……………………………………………………………………………………
D THE ELECTRONIC STRUCTURE OF AN ATOM
Learning Outcomes
You should be able to:
describe electron arrangements of elements with proton numbers 1 to 20,
draw electron arrangement of an atom in an element,
state the meaning of valence electrons,
determine the number of valence electrons from the electron arrangement of an atom.
Activity 6
1. Electrons are filled in specific shells, starting with the shell nearest to the nucleus of the atom.
Every shell can be filled only with a certain number of electrons.
The first shell can be filled with a maximum of ……………. electrons
The second shell can be filled with a maximum of ……………. electrons
The third shell can be filled with a maximum of …………….electrons
Use ‘x’ as symbol for
electrons. Draw the maximum
number of electrons in each
shell.
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9. WAJA F4 Chemistry 2010 Chapter 2: The Structure of Atom
23
2(a) Draw the electron arrangement of a sodium atom, 11 Na in the box and complete the table given.
Number of protons
Number of electrons
Number of neutrons
Proton number
Nucleon number
Electron arrangement
(b) Draw the electron arrangement of a chlorine atom, Cl in the box and complete the table given.
Number of protons
Number of electrons
Number of neutrons
Proton number
Nucleon number
Electron arrangement
x
x
3 Valence electrons are electrons in the ………………..………… shell of a neutral atom.
4 Identify the number of valence electrons in these atoms according to its electron arrangement.
Atom of Element Electron Arrangement Number of valence electrons
Oxygen 2.6
Aluminium 2.8.3
Chlorine 2.8.7
Neon 2.8
Potassium 2.8.8.1
Magnesium 2.8.2
Carbon 2.4
Phosphorus 2.8.5
Helium 2
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