Formulae and equations

Water H20                                 Carbon dioxide CO2               Sulphur dioxide SO2

Methane CH4                            Hydrochloric acid HCl             Sulphuric acid H2SO4

Nitric acid HNO3                       Ethanoic acid CH3CO2H        Ammonia NH3

Ammonium chloride NH4Cl      Sodium hydroxide NaOH        Sodium chloride NaCl

Sodium carbonate Na2CO3     Sodium hydrogencarbonate NaHCO3

Sodium sulphate Na2SO4        Copper (II) oxide CuO        Copper (II) sulphate CuSO4

Calcium hydroxide Ca(OH)2     Calcium carbonate CaCO3    Calcium chloride CaCl2

Positive:

Ammonium (NH4)+          Hydrogen (H)+             Lithium (Li)+               Potassium (K)+

Sodium (Na)+                   Silver (Ag)+                 Barium (Ba)2+            Calcium (Ca)2+

Magnesium (Mg)2+          Copper (II) (Cu)2+        Iron (II) (Fe)2+            Iron (III) (Fe)3+

Aluminium (Al)3+

Negative:

Bromide (Br)-            Chloride (Cl)-               Fluoride (F)-                Iodide (I)-

Hydrogencarbonate (HCO3)-          Hydroxide (OH)-          Nitrate (NO3)-           

Oxide (O)2-               Sulphide (S)2-              Carbonate (CO3)2-     

Sulphate (SO4)2-        Phosphate (PO4)3-

Redox is when electrons are transferred. Something will be reduced, and something else will be oxidised.

Oxidation is the addition of oxygen and the loss of electrons. It acts as a reducing agent.

Reduction is the loss of oxygen and the gain of electrons. It acts as an oxidising agent.

Rules: 

• Oxidation number of an uncombined element is zero.
• Sum of the oxidation numbers in a compound is zero - in an ion the sum equals the overall charge.
• In compounds the oxidation numbers of Group 1 metals is +1 and Group 2 metals is +2.
• Oxidation number of fluorine is always -1.
• Oxidation number of oxygen is -2 - except with fluorine or in peroxides (-1) or superoxides.
• Oxidation number of hydrogen is +1 - except hydrogen in metal hydrides is -1.
• Oxidation number of halogen in metal halides is always -1.
• Chemical species with atoms of more than one element, the most electronegative element is given the negative oxidation number.

Ionic compounds

1. Write the symbols of the ions in the compound.

2. Balance the ions so that the total of the positive and negative ions adds to zero.

3. Write the formula without the charges and put the number of ions of each element as a small number following and below the element symbol. 

Chemical equations

1. Write the symbols and formulae for the reactants and products.

2. Balance the equation by multiplying formulae if necessary and add state symbols.

Ionic equations

1. Write out the chemical equation and then only (aq) compounds as ions underneath.

2. Cancel unchanged ions as they are spectator ions.