LESSON 1; THE HISTORY OF ATOMIC THEORY

Leucippus
● Ancient greek philosopher
● Around 40 years older than Democritus
● ‘What is matter made up of?’
● Model of atom as a sphere created by him
Democritus
● Ancient greek pre-socratic philosopher , 460 - 370 BC
● Primarily remembered today for his formation of the atomic theory of the
universe
Democritus Theory
1. All matter consists of invisible particles called atoms
2. Atoms are indestructible
3. Atoms are solid but invisible
4. Atoms are homogeneous
5. Atoms differ in size, shape, mass, position and arrangement
● Solids are made of small, pointy atoms
● Liquids are made of large, round atoms
● Oils are made of very fine, small atoms that can easily slip past one another
Plato & Aristotle
● Disagreed upon democritus’ theory, believed it was continuous
● Plato 427-347 BC
● Aristotle 384-322 BC
John Dalton
● 1766-1844
● First to actually experiment in attempt of proving his beliefs
Dalton’s Atomic Theory
1. The elements are made of atoms, which
are tiny particles, too small to see
2. All atoms of a particular element are
identical
3. Atoms of different elements have
different properties: their masses are different,
and their chemical reactions are different
4. Atoms cannot be created, destroyed, or
split
5. In a chemical reaction, atoms link to one
another, or separate from one another
6. Atoms combine in simple whole-number
ratios to form compounds
G J Stoney
● 1826-1911
● discovered + coined electrons
J J Thomson
● 1856-1940
● 1897, discovered that electrons had mass + charge
Cathode Ray Tube vacuum tube containing 1 or more electron guns, which emit
electron beams that are manipulated to display images on a phosphorescent screen.
The images may represent electrical waveforms, pictures, radar targets, or other
phenomena.
Phosphorescent light given off at low temps that is caused by the absorption of
radiations (X Rays/ultraviolet light) + continuing a noticeable time after these
radiations have stopped
Thomson’s Plum Pudding Model

Ernest Rutherford
● 1871-1937
● Discovered in 1911 that the atom is a mostly empty space w a small dense
positively charged nucleus
Rutherford’s Model
Niels Bohr & His Model

● 1855-1962
● discovered electrons spin
around the nucleus in different
energy levels/shells

James Chadwick
● 1891-1974
● Discovered the neutron
● Nobel prize winner
● Worked on WW2 atomic
bomb
Protons positively charged
Neutrons neutrally charged
Electrons negatively charged

LESSON 2; ATOMIC STRUCTURE

Atomic number # of protons in the nucleus of an atom
Elements pure substance made up of only one type of atom
Neutrons number of neutrons are not always the same
Mass number # of protons + neutrons together, # of particles in the nucleus
Nucleus central part of an atom , # of protons + neutrons
Electron shells regions around the nucleus where the electrons are found

LESSON 3; ELECTRON CONFIGURATION

Niels Bohr
● 1855-1962
● 1913, discovered electrons spin around the nucleus in different energy
levels/shells
Electron shells
● Maximum number of electrons in a shell : 2, 8, 18, 32
● Pre-ATAR simplification ^ : 2, 8, 8, 2
 ● Tend to fill lowest/first energy level first before starting other levels
● Electrons symbolised as an X & in pairs, nucleus is a element symbol
Inert Gases full outer shell + doesn’t react
● All neutral atoms have the same number of electrons as they do protons.
They have the same number of negative charges as positive charges. In
the simplest atom, the hydrogen atom, there is one proton and one
electron.
● Electrons are arranged in energy shells.
● Electrons will fill the lowest energy shell first and then go to the second
shell. Only when the second energy shell has 8 electrons will another level
start.
● Inert gases have a full outer shell. They are the gases with least reactivity
or no reactivity at all. They are also called Noble gases.

1. All matter is made of atoms which are composed of protons, neutrons and
electrons.
2. The atomic number is the number of protons in the nucleus of an atom.
3. In an atom, the number of protons is the number of electrons.
4. The number of neutrons in an atom are not always the same.
5. The atomic number is the number of protons and neutrons together. It is the
number of electrons in the nucleus.

LESSON 4; FLAME TESTS

1. All neutral atoms have the same number of electrons as they do protons.
They have the same number of negative charges as positive charges.
2. Electrons are arranged in energy shells.
3. Electrons will fill the lowest energy shell first and then go to the second shell.
Only when the second energy shell has 8 electrons will another level start.
4. Inert gases have a full outer shell. They are the gases with least reactivity or
no reactivity at all. They are also called noble gases.

● The electron arrangement of an atom can change when exposed to heat, light
or electricity.
● When an electron absorbs energy, it enters what is known as an excited state.
● When an electron is in the lowest energy level, it is said to be in ground state.
● When an electron drops back down to its ground state, it releases the extra
energy in the form of light.
● We can identify an element by observing the colour of light it produces when it
drops back down to its ground state.
Excited state the state in which an atom is after gaining energy
Ground state the state of an atom when its electrons are in their lowest possible
energy levels
Ion
● atoms or groups of atoms that have lost or gained electrons
● Positive = lost electron
● Negative = gain electron

LESSON 5; THE PERIODIC TABLE

1. The electron arrangement of an atom can change when exposed to heat, light
or electricity.
2. When an electron absorbs energy, it enters what is known as an excited
state.
3. When an electron is in the lowest energy level, it is said to be in ground state.
4. When an electron drop back down to its ground state, it release the extra
energy in the form of light.
5. We can identify an element by observing the colour of light it produces when
it drops back down to its ground state.
Triads
● 3 ‘tri’ elements
● E.g. chlorine, bromine, iodine, and calcium, magnesium, beryllium
Dmitri Mendeleev
● 1834-1907 russian
● Created the framework for the modern periodic table
Groups columns of the periodic table 1-18
Periods rows of the periodic table 1-7
Periodic Law statement made by Mendeleev that elements with similar properties
occur at regular intervals when all elements are listed in order of atomic mass
A = the mass number
= number of protons + number of neutrons
Z = the atomic number
= number of protons
= number of electrons (for a neutral atom)
E = the symbol of the element.
 LESSON 7; PRACTICAL FAMILIES OF METALS
Atoms in the same group of the periodic table have similar properties because
they have the same number of electrons in their outer shells.

LESSON 8; METALS, NONMETALS & METALLOIDS

Metals
● solid at room temperature except mercury
● lustre (shiny)
● good conductors
● malleable (can be moulded)
● ductile (can become wires)
● high melting point except for group 1
Non-Metals
● gas/liquid at room temp
● dull
● brittle
● poor conductors
● low melting point
Metalloids
● Have both properties of non metal & metal
● e.g. silicone, can be polished but poor conductor

LESSON 9; IONIC BONDING

1. What are the six main properties of metals?
Moldable, Shiny, Solid at room temperature, good conductor, high melting point,
ductile
2. What are the five main properties of non-metals?
Dull, liquid or gas at room temperature, brittle, poor conductor, low melting point
3. What are the properties of metalloids?
Mix of metal and non metal
Noble Gases
● full outer shell of electrons ; helium 2, neon 2,8, argon, 2,8,8
● stable and doesn’t react
Ionic Bonding
● when a metal combines with a non-metal
● atoms lose or gain electrons to become charged ions
● electronic configuration of noble gases
Metallic atoms ; smaller number of electrons in outermost shell
● Sodium 2,8,1
● Magnesium 2,8,2
● Calcium 2,8,8,2
They lose electrons to obtain noble gas configuration
● Sodium 2,8
● Magnesium 2,8
● Calcium 2,8,8
Since atoms lost negative charges they are now positive [ions]
● Sodium = 11 proton, 10 electron (+11 - 10 = +1)
● Magnesium = 12 proton, 10 electron (+12 - 10 = +2)
● Calcium = 20 proton, 18 electron (+20 - 18 = +2)
Non-metallic atoms ; higher number of electrons in outermost shell
● Oxygen 2,6
● Fluorine 2,7
● Chlorine 2,8,7
They gain electrons to obtain noble gas configuration
● Oxygen 2,8
● Fluorine 2,8
● Chlorine 2,8,8
Since atoms gained negative charges they are now negative [ions]
● Oxygen = 8 protons, 10 electrons (+8 - 10 = -2)
● Fluorine = 9 protons, 10 electrons (+9 - 10 = -1)
● Chlorine = 17 protons, 18 electrons (+17 - 18 = -1)
Making Compounds
● Atoms combine to form compounds
● Outer shell is involved when bonding
● Combined atoms are more stable
Ionic Compounds
● positive + negative ions
● Solid at room temp + pressure
● High melting points due to strong ionic bonds
● Usually soluble in water
 ● Aqueous solutions conduct electricity
Chemical/Molecular Bond the link that holds atoms together in a substance
Compound substance made up of two or more different types of atoms that have
been joined (bonded) together
Cations positively charged atoms
Anions negatively charged atoms

LESSON 10; COVALENT BONDING

● When the outer shell electrons of atoms interact, atoms can become
chemically joined together to form molecules. The join is called a ionic
bond.
● When atoms combine, they form compounds and become more stable.
● The most stable elements in the periods table are noble gases.
● Ionic bonds occurs when a metal combines with a nonmetal.
● Ionic compounds usually form groups of positive and negative ions rather
than individual molecules.

Noble gases inert gases

● stable and does not react
● Full outermost shell of electrons
● Helium 2
● Neon 2,8
● Argon 2,8,8
Nonmetals
● Higher number of electrons in outermost shell
● Oxygen 2,6
● Fluorine 2,7
● Chlorine 2,8,7
● Share electrons upon combining
● They obtain noble gas electron structure by their shared electrons
Covalent molecules
● Usually gases or liquids at room temp + pressure
● Low melting and boiling points
● Usually insoluble
● Does Not conduct electricity