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Atoms
What are atoms
 An atom has a nucleus in the centre and is
surrounded by electrons.
 The nucleus is positively charged
 The electrons are negatively charged
 The atom is neutral.
 Nucleus is made up of protons and neutrons.
 An atom is neutral because it has the same
number of electrons and protons.
Atomic Number
 The Atomic number = Number of protons
Mass Number
 The Mass Number = number of protons +
neutrons.
Isotopes
Isotopes are different forms of the same element with the
same number of protons but different number of neutrons
Elements
 There are about 100 elements
 It cannot be broken down chemically
 It contains the same type of atom
 They are arranged in ascending atomic number in
the periodic table
Compound
 A compound is a substance that contains at least
two elements chemically combined
Electronic configuration
 Electrons occupy shells around the nucleus.
 Electronic configuration:
 Shell 1 – 2 electrons
 Shell 2 – 8 electrons
 Shell 3 – 8 electrons
 Shell 4 – 8 electrons etc.
Group 1 Metals
• They are known as alkali metals
• Examples are _______________________
Reactions
• They are stored under oil because they react with air and
water.
• They have _____ electron in their outer shell
• Group 1 metals have similar properties because they have
the same number of electrons in their outer shell
• Alkali metals have similar properties because when they
react, an atom loses one electron to form a positive ion
with a stable electronic structure
ionic equation –
• They more reactive the alkali metal the easier it is for an
atom to lose one electron.
• This is known as oxidation.
Reactions with Metals
• Group 1 metals react vigorously with water.
• Hydrogen is formed
• An alkali is formed which is the hydroxide of the metal
• Reactivity increases down the group
• Word equation =
• Balanced equation =
Reactivity
• Order of reactivity is:
1. Potassium
2. Sodium
3. Lithium
Flame tests
• Lithium – Red
• Sodium – Yellow
• Potassium – Lilac
Group 7
 Group 7 elements are known as halogens
 Examples are ______________________
Physical properties
 Chlorine is a green gas
 Bromine is an orange liquid
 Iodine is a grey solid
Uses
 Chlorine – to sterilise water
 Chlorine to make pesticides and plastics
 Iodine is used to sterilise wounds (antiseptic)
 Sodium chloride (salt) is used
– As a preservative
– As a flavouring
– To manufacture chlorine
Reactions
 Group 7 elements have similar properties because
they have ____ electrons in their outer shell
 React vigorously with alkali metals to produce
metal halides
 Halogens have similar properties because when
they react, an atom gains one electron to form a
negative ion with a stable electronic structure
 Write an equation to show the formation of a
halide ion from a halogen molecule
 The more reactive the halogen the easier it is for
the atom to gain one electron
The gain of electrons is called reduction
Reactivity - The order of reactivity is :
– Fluorine
– Chlorine
– Bromine
– Iodine
Therefore reactivity decreases down the group
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Electrolysis
• The anode is the positive electrode
• The cathode is the negative electrode
• Anions are negative attached to the anode
• Cations are positive ions attached to the cathode
• An electrolyte is the liquid which conducts
electricity
Sulphuric acid solution
• Sulphuric acid solution can be broken down by
electrolysis into hydrogen and oxygen
• Hydrogen (+ve) is made at the cathode (negative
electrode)
• Oxygen (-ve) is made at the anode (positive
electrode)
Test for gases
• Test for hydrogen = burns with a ‘pop’ when lit
using a lighted splint
• Test for oxygen = relights a glowing splint
Aluminium
• Aluminium is extracted from its minerals using
electricity
• Electrolysis is the decomposition of a liquid using
electricity
• Bauxite is a mineral containing aluminium. It is
molten aluminium oxide.
• Oxygen is formed at the graphite anode
• Anodes are gradually worn away by oxidation
• Aluminium is formed at the graphite cathode
• Process has a high electrical energy requirement
• Cryolite is used to lower the melting point of the
aluminium oxide
• Aluminium is expensive because its extraction
uses large amounts of electricity
Metals
• Iron is used to make steel and to make cars and bridges
because it is strong
• Copper is used to make brass and to make electrical wiring
because it is a good electrical conductor.
Physical properties of metals
• Lustrous, hard and high density
• High tensile strength
• High melting & boiling point due to strong metallic bonds
• Good conductors of heat and electricity
• Particles in a metal are held together by metallic bonds
Properties
• Properties needed by a metal for a particular given use e.g.
Saucepan bases need to be good conductors of heat
Crystals
• Metals have a structure which contains crystals
• Particles in solid metals are close together and in a regular
arrangement
• At low temperatures some metals can be superconductors.
Metallic bonding
• This can be described as strong electrostatic attraction
between a sea of delocalised electrons and close packed
positive metal ions
• This explains why metals have high melting and boiling
points – because of the strong attraction between the
delocalised electrons and the positive metal ions needs to
be overcome.
Electricity
• When metals conduct electricity electrons move
• These are delocalised electrons
Superconductors
• Materials that conduct electricity - little or no resistance
• They can be powerful electromagnets
• However they only work at very low temperatures
Transition Elements
Examples
 Copper = Cu
 Iron = Fe
 All transition elements are metals and have
typical metallic properties
Colours
• Compounds of transition elements are often
coloured
– Copper compounds are blue
– Iron II compounds are light green
– Iron III compounds are orange/brown
Catalysts
• Transition elements and their compounds are
often catalysts
– Iron in the Haber process
– Nickel in the manufacture of margarine
– A catalyst _______ up the rate of a
reaction.
But it does not get used up.
Thermal Decomposition
• This is a reaction in which a substance is broken
down into at least two other substances by heat.
• It usually results in a colour change
Precipitation
• Reaction between solutions that makes an
insoluble solid
• Sodium hydroxide solution is used to identify the
presence of transition metal ions in solution:
– Copper ion = blue solid
– Iron II ion = green solid
– Iron III ion = orange solid
These are all solid precipitates
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