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Contents
Unit 1: Bonding
Unit 2: Structures and Properties
Unit 3: Chemical Calculations
Unit 4: Rates of Reaction
Unit 5: Energy and Reactions
Unit 6: Electrolysis
Unit 7: Acids, Alkalis and Salts

[This is Unit 2 Chemistry, Additional Chemistry. This section comes after Core
Chemistry in an AQA Course (Unit…

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Electronic Configuration
The electrons in atoms are arranged in shells, but each shell can only hold a certain
number of electrons:

The first shell can hold only 2 electrons
The second shell can hold up to 8 electrons
The third shell can also hold 8 electrons

Sodium (Na) has a…

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The diagram shows the formation of sodium chlorine (NaCl). The lone electron on
the outer shell of the sodium atom is lost to complete the outer shell of the chlorine
atom. This results in the sodium atom now becoming an ion (Na+) and the chlorine
atom now becoming a negative…

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covalent bonds joined together - these are the giant covalent structures. Examples of
giant covalent structures are diamond and silicon dioxide (silica).

Metallic Bonding
Metals can bond using metallic bonding, which tends to produce more giant
structures also. You can consider metals as a lattice of metal atoms (or positively…

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Remember OILRIG:
Oxidation Is Loss of electrons;
Reduction Is Gain of electrons

An ionic solid will not conduct electricity because the ions are in a fixed
position
A molten ionic compound will conduct electricity because ions are free to
move
An ionic compound in solution will also conduct electricity

Covalent…

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The atoms in the giant structure of diamond (left) are held together by extremely
strong covalent bonds. It has some special properties which other types of structure
do not possess. It is very hard, has high melting/boiling points and is very chemically
unreactive.

Another type of giant is a fullerene,…

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helium atoms with a mass number of 4 is said to have an equal mass to one carbon
atom (mass number 12) - because of relative atomic mass. Because atoms lose
electrons when becoming ions, it tends not to affect its relative atomic mass,
because the weighting of electrons in…

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Empirical Formulae
If you are given the percentage formula of an element in a compound, we can work
backwards and find the ration between the atoms in the compound. We call this
ratio the empirical formula, which is simply a compound stated in its simplest form
of ratio between the…

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(5 ÷ 24) x 40g = 8.33g of MgO
We can also do it by calculating the proportion of the amounts from the equation:
5 x (80 ÷ 48)g = 8.33g of MgO

We use the term yield to compare how much is actually made in a chemical reaction
with…

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The Haber Process
We use a special process to make ammonia, called The Haber Process. This
ammonia can be used to make fertilisers and other commercial chemicals. There are
two reactants in the process:
- nitrogen from the air, and,
- hydrogen (usually obtained from natural gas)
These reactants are…

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