1. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/Faridahhamat/SASER 2006
THEME : MATTER AROUND US
LEARNING AREA : 2. THE STRUCTURE OF THE ATOM
2.1 Analysing matter
2.2 Synthesising atomic structure
2.3 Understanding isotopes and assessing their importance
2.4 Understanding the electronic structure of an atom
2.5 Appreciate the orderliness and uniqueness of the atomic structure
A Matter
PARTICULATE NATURE OF MATTER
1.0 Introduction
What is matter?
 Matter is anything that occupies space and has mass
 Matter is made up of very tiny discrete particles.
 These particle can be atoms, molecules and ions
[ATOM is the smallest particle of an element. MOLECULE is a group of two
or more atoms which are chemically bonded together. ION is an atom or a
group of atoms carrying an electric charge. An ion is a positively-charged or
negatively-charged particle]
MATTER
ELEMENT COMPOUND
METALS NON METALS IONIC COVALENT
COMPOUND COMPOUND
ATOM ATOM MOLECULE
M ION MOLECULE
Sodium Helium Hydrogen NaCl H2O
Iron Argon Oxygen PbBr2 NO2
Lead Krypton Nitrogen MgO CO2
Copper neon Chlorine CuSO4
CO
Tin Bromine
Silver iodine NH3
Zinc
Lithium

2. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/FH/SASER 2006
 All substances can be classified into three states of matter; namely solid,
liquid and gas
Solid  Fixed volume
 Fixed shape
Liquid  Fixed volume
 No fixed shape. Takes the shape of the container
it is in
Gas  No fixed volume
 No fixed shape. Takes the shape of the container
it is in
2.0 The State of Matter
1. Matter can exist in three physical states: Solid, liquid and gas.
2. Differences between solid, liquid and gas
Property Solid Liquid Gas
Arrangement  Very 
Closely  Very far
of particles closely packed apart from
packed  Disorderly each other
 Orderly arrangeme  Random
manner nt motion
Forces of Very strong Strong forces of Very weak forces
attraction forces of attraction of attraction
between attraction between particles between particles
particles between particles but weaker than
the forces in solid
Motion of Vibrate and rotate Particles can Particles can
particles about a fixed vibrate, rotate and vibrate, rotate
position move throughout and move freely.
the liquid. The rate of
collision is
greater than the
rate of collision in
liquid.
Diagrammatic
representatio
n of the
particles in
each of the
physical
states
Energy Low Moderate High
content
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3. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/FH/SASER 2006
Kinetic Particle Theory
1. The kinetic particle theory is a model to explain the properties of matter
2. The main points of this theory are:
 All matter is made up of tiny discrete particles
 The particles in matter are always in motion
 The kinetic energy of a particle changes with temperature
 The average kinetic energy of all particles is directly proportional to
the absolute temperature
3.0 Changes in state
GAS
Boiling
Sublimation Condensation
Melting
SOLID LIQUID
Freezing
Figure 1 : States of matter
Using Kinetic Particle Theory to explain Changes in states of matter
1. Solid to Liquid
When a solid is heated, the particles in the solid gain kinetic energy and
vibrate more vigorously. The particles vibrate faster as the temperature
increases until the energy they gained is able to overcome the forces that
hold them at their fixed positions. At this point, the solid becomes a liquid.
This process is called melting. The temperature at this point is called the
melting points
2. Liquid to Gas
When a liquid is heated, its particles absorb the heat energy and move at
a faster rate. The kinetic energy of the particles increases. The particles
move further apart from one another. When the kinetic energy is enough
to overcome the forces of attraction among the liquid particles, liquid
changes into gaseous state. At this point, the liquid becomes gas. This
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4. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/FH/SASER 2006
process is called boiling. The temperature at this point is called the
boiling points
3. Gas to Liquid
When a gas is cooled, the particles in the gas lose energy and move
slower. As the temperature continues to drop, the particles continue to
lose more energy until they do not have enough energy to move freely. At
this point, the gas becomes liquid. This process is called condensation.
The temperature at this point is called the boiling points
4. Liquid to Solid
When a liquid is cooled, the particles in the liquid lose energy and move
slower. As the temperature continues to drop, the particles continue to
lose more energy until they do not have enough energy to move freely. At
this point, the liquid becomes a solid This process is called freezing. The
temperature at this point is called the freezing points
Temperature, oC
D
liquid
B Solid + liquid
Solid C
A
Time, minute
Figure 2: Heating curve
At point AB: Naphthalene exists as solid. When solid naphthalene is heated,
heat energy is absorbed. This causes the particles to gain kinetic energy and
vibrate faster. This is why the temperature increases from point A to point B
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5. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/FH/SASER 2006
At point BC: Solid naphthalene begins to melt. During the melting process, the
temperature of matter does not rise, even though heating continues. The
temperature remains constant because the heat energy absorbed by particles
is used to overcome the forces between solid particles. This constant
temperature is the melting point and both solid and liquid are present.
At point CD: All the solid has melted (liquid state). From point C to D, the
particles in liquid absorb heat energy and move faster. The temperature
increases from point C to point D
Temperature, oC
E
F G
H
Time, minute
Figure 3: Cooling curve
At point EF: Naphthalene is in the liquid state only. When liquid is cooled, the
naphthalene molecules lose heat energy. Their movement shows down and they
move closer to each other
At point FG: The liquid begins to change into a solid form. There is a mixture of
solid and liquid state here. The temperature remains constant because the heat
loss to the surroundings is exactly balanced by the heat energy liberated
as the particles attract one another to form a solid. The temperature remains
constant until all the liquid changes to solid. This is the freezing point of
naphthalene. The molecules lose heat and form stronger forces of attraction.
Molecules rearrange to form the molecular arrangement of a solid.
At point GH: Once all the liquid has become solid, the temperature falls once
again until it reaches room temperature. Naphthalene is in the solid state here.
The particles in the solid vibrate slower as the temperature decreases
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6. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/FH/SASER 2006
4.0 Diffusion
Diffusion occurs when particles of a substance move in between
the particles of another substance.
a) Gas Diffusion
Air (colourless) Gas jar
Reddish-brown
Cover vapour spreads
Cover is throughout both
Reddish brown removed gas jars after
Bromine vapour some time
Figure 1 : Diffusion of Bromine gas
 The bromine particles move in between the air particles
 The bromine particles have diffused throughout the air particles
b) Liquid Diffusion
Purple colour
Distilled water spread slowly
until after several
hours, the whole
Potassium After some
solution turns
Manganate(VII) crystal time
purple
 Potassium manganate(VII) crystals dissolve in water to produce a
solution containing potassium ions, K+ and manganate ions, MnO4-
 These ions move randomly in water
 K+ and MnO4- ions move and fill up the empty spaces found in
between water molecules
 Diffusion is slower because there are less empty spaces in liquids
than in gases
c) Solid Diffusion
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7. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/FH/SASER 2006
Jelly
CuSO4 particle
The blue color spreads
very slowly upwards
through the jelly
 Copper(II) sulphate crystals are made up of Cu2+ and SO42- ions.
 These ions move upwards and occupy the empty spaces in
between jelly particles.
 Diffusion is much slower in solids because solid particles are
arranged compactly with very little space between particles
B The Atomic Structure
The Historical development of atomic models
Scientist Model Characteristics
John Dalton  Atom as a small, indivisible
(1803) ball similar to a very tiny ball
 Atom cannot be created nor
destroyed
 All atom of a particular
element are the same (have
the same mass and physical
features)
Weakness
 Smaller particles are called
subatoms
 Atom can be created and
destroyed ( nuclear reaction)
 Atom of the same element
can have different physical
features (isotopes)
J.J  He discovered electron
Thomson’s  The atom as a sphere of
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8. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/FH/SASER 2006
(1897) positive charge which
contains a few negatively
charge particles called
electrons
Ernest  He discovered proton
Rutherford  The positive charge and
(1871 – 1937) most of the mass of the atom
are concentrated in a small,
central region called nucleus
 Electron moves outside the
nucleus
 Most parts of the atom
contain empty space
Weakness
 The atomic mass calculated
using this model is lesser
then the actual atomic mass
of an element
Neil Bohr  The electrons move in
(1885 – 1662) shells around the nucleus
 Each orbit is at a fixed
distance from the nucleus
James  Proved the existence of
Chadwick neutrons, the neutral
(1891-1974) particles in the nucleus
 Neutrons contribute
approximately to half the
mass of an atom
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9. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/FH/SASER 2006
Subatomic particles of an atom
 An atom contains three types of subatomic particles: proton,
neutron and electron.
 Proton and neutron are found in the nucleus
 Electrons move around the nucleus in fixed orbits
Particles Symbol Relative charge Relative mass
Proton p +1 1
Neutron n 0 1
Electron e -1 1/1840
Proton Electron
Nucleus
Neutron
 The nucleus is positively charged because of the presence of
protons, which are positively charged
 Neutrons are neutral
 Atom contains the same number of electron as the proton
because atom is a neutral particle
Proton Number and Nucleon Number
 Proton number of an element is the number of protons in its atom
 Nucleon number of an element is the total number of protons and
neutrons in its atom
Nucleon Number = number of protons + number of neutrons
Nucleon Number = Proton Number + number of neutrons
Nucleon number A
Symbol of
X element
Proton Number Z
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10. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/FH/SASER 2006
C Isotopes
Meaning: Isotopes are atoms of the same element containing the same
number of protons but different numbers of neutrons
[Isotopes are atoms of the same element containing the same proton
numbers but different nucleons number]
Examples:
a) Oxygen – 16 has 8p, 8e, 8n
Oxygen - 17 has 8p, 8e, 9n These three different atoms
Oxygen – 18 has 8p, 8e, 10n contain 8 protons. This
determines that all atoms are
oxygen atom
b) Carbon – 12 has 6p, 6e, 6n
Carbon – 14 has 6p, 6e, 8n
Properties
Isotopes have the same chemical properties (because they have
the same number of protons) but slightly different physical properties
such as melting point and density
Uses of isotopes in daily life
 Iodine -131 used to detect Goiter (penyakit beguk)
 Carbon – 14 used to determine age of fossil based on the quantity
of carbon -14
 Cobalt – 60 used in radiotherapy for treatment of cancer (to kill the
cancer cell)
 Gamma rays of cobalt-60 are used to destroy bacteria in food
without changing the quality of food
 The metabolism of phosphorus in plants can be studied using
phosphate fertilizers that contain phosphorus-32
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11. LESSON NOTES/CHAPTER 2/CHEMISTRY PANEL/FH/SASER 2006
D The Electronic Structure of an Atom
 Electron Arrangement of an atom is the arrangement of electron
in shells (orbits) around that atom’s nucleus
(The electrons in an atom are arranged in shells around the
nucleus)
 The maximum number of electrons which can fill a particular shell is
as follows:
Shell Maximum number
of electron
1st 2
nd
2 8
rd
3 8 or 18
4th 36
 For atoms with proton numbers of 1 to 20, two electrons can
occupy in the first shell, eight electrons in the second shell and
eight electrons in the third shell
[ Electrons occupy the shells closest to the nucleus first. They only
start occupying a new shell when the previous one has been occupied]
Electron
First shell
Nucleus
Second shell
Third shell
Figure 1: Neon atom
 Valence electron
The electrons in the outermost occupied shell are known as
valence electrons
There are 8 electrons in the outermost occupied shell of the
neon atom in Figure 1. Therefore, the valence electrons of a
neon atom is 8
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