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GCSE CHEMISTRY REVISION

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
charge
Proton +1

Neutron 0

Electron -1




All atoms of the same element have the same number of protons…

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number of electrons in their outer shell, and therefore have the same
properties.

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 ­…

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l2 ). 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…

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Methane (CH4)




Oxygen (O2)

O­O




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…

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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…

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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
atom.
Number of neutrons = mass number ­ atomic number
The number of electrons is equal to…

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24 + 16 = 40 ( M r)
24
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…

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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…

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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.
Calcium carbonate Calcium oxide + Carbon dioxide
CaCO3 CaO + CO2
M r of CaCO3 = 40 + 12 + (3x16) =…

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compromise.

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. Factors that affect the rate of reaction ­
Temperature
Concentration
Surface area
Use of catalyst

Temperature of…

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