Oxidation & Reduction in Terms of Electrons (Oxford AQA IGCSE Chemistry)

Oxidation & Reduction in Terms of Electrons

• As well as understanding oxidation and reduction in terms of oxygen, you need to understand these reactions in terms of electrons

• When a substance loses electrons it is oxidised

• When a substance gains electrons it is reduced

• If this occurs in the same reaction, the reaction is a redox reaction

• For example, when iron reacts with a compound of copper such as copper sulfate, a displacement reaction occurs

iron + copper sulfate → iron(II) sulfate + copper 

Fe + CuSO₄ → FeSO₄ + Cu

• We can write this as an ionic equation

Fe + Cu²⁺ + SO₄^2– → Fe²⁺ + SO₄^2– + Cu

• We can then remove the spectator ions to see the overall change

Fe + Cu²⁺→ Fe²⁺ + Cu

• The iron has lost electrons to become a positive ion, so has been oxidised

• The positive copper ion has gained electrons to become an atom, so have been reduced

The redox reaction between Fe and Cu²⁺