AQA Chemistry 2

Everything you need for the AQA Chemistry 2 exam

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  • Created on: 21-05-12 16:17
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Atomic Structures
Atoms have a small central nucleus made
up of protons and neutrons; electrons
surround the nucleus. They all have
relative electric charges ­
Atomic particle Relative
Proton +1
Neutron 0
Electron -1
All atoms of the same element have the same number of protons and electrons.
The atomic number represents the number of protons in an element.
Electron Configuration
This tells us how the electrons are arranged in shells
around the nucleus.
The first shell can only contain a maximum of 2 electrons.
The shells after this can contain a maximum of 8 electrons.
Electronic Structure
In the periodic table elements are arranged depending on the number of
elements in their outer shell. Elements in the same group have the same

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Mixtures and Compounds
A mixture is two or more elements/compounds that are not chemically bonded.
A compound is a substance where the atoms of two or more elements are
chemically combined.
Atoms form chemical bonds by ­
Sharing electrons (covalent bonds)
Gaining/losing electrons (ionic bonds)
When an atom forms chemical bonds the outer most shell becomes complete
with electrons.
Ionic Bonding
This happens between metals and non-metals and involves the transfer of
electrons.…read more

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The calcium has 2 electrons on its outer shell to begin with and the
chlorine has 7 so only needs one, therefore 2 chlorine atoms are needed to get
ride of the 2 electrons. Calcium then becomes C a2+ and the 2 chloride ions
become C l- there for it makes CaC l2 .
Covalent Bonding
This is a very strong bond, which is formed when electrons are shared. This
occurs between non-metal atoms.…read more

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Methane (CH4)
Oxygen (O2)
Giant covalent structures
Diamond is a form of carbon that has a giant,
ridged covalent structure, also known as a
lattice. Each carbon atom forms a covalent bond
with other carbon atoms. This large number of
covalent bonds results in diamond having a
very high melting point and being very hard.…read more

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A giant ionic structure is a regular structure held
together by the strong forces of attraction between
oppositely charged ions. These forces act in all
directions of the lattice. This results in them having
high melting and boiling points.
Ionic compounds also conduct electricity when
molten or in a solution as the charge ions are free to
move and carry a current.
Metals have a giant structure in which electrons can be delocalised.…read more

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The mass number is the top number; it is the umber of protons and neutrons in
an atom.
The atomic number is the bottom number; it is the number of protons in the
Number of neutrons = mass number ­ atomic number
The number of electrons is equal to the number of protons (atomic number)
because atoms have no overall charge so they have the same umber of electrons
and protons.…read more

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M r)
40 x 100 = 60
60% magnesium in magnesium oxide
Calculating empirical formulae of a compound
This is the simplest formula that represents the composition of the compound
by mass.
Example ­ Find the simplest formula of an oxide of iron produced by reacting
1.12g of iron with 0.48g of oxygen
Fe = 1.12g
O = 0.48g
First divide each mass by there relative atomic mass
Fe = 56 = 0.02
O= 16 = 0.…read more

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As we are only being asked for calcium oxide and calcium carbonate, so
we just need the ration of those two.
100 : 56
If 100kg of C aCO3 produces 56kg of C aO
Then 1kg of C aCO3 produces 0.56kg of C aO
So 50kg of C aCO3 produces (0.56x50) 28kg of C aO
Calculating the mass of a reactant
Example ­ calculate how much aluminium oxide is needed to produce 540
tonnes of aluminium.…read more

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Example ­ calcium oxide is the useful product as it can be used to produce
slaked lime, carbon dioxide is also produced but this is a waste product.…read more

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Rate of reaction
Chemical reactions only occur when reacting particles collide with each other
with enough energy. The minimum about of energy needs to cause a reaction is
called the activation energy.…read more


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