OxidatIon & Reduction in Terms of Electrons (OCR GCSE Chemistry A (Gateway)): Revision Note

Oxidation & Reduction in Terms of Electrons

Higher Tier Only

• For reactions not involving oxygen, we can look at oxidation and reduction in terms of losing and gaining electrons

• Oxidation is the loss of electrons

• Reduction is the gain  of electrons 

• We can use half and ionic equations to determine which species has been oxidised and reduced in terms of electrons 

• A displacement reaction occurs between magnesium and copper sulfate: 

Mg (s) +  CuSO₄ (aq) →   MgSO₄ (aq) + Cu (s) 

• The  ionic equation for this reactions is:

Mg (s) + Cu²⁺ (aq)  → Mg²⁺ (aq)  + Cu (s)

• This can be split into two half equations which demonstrate oxidation and reduction individually:

Mg → Mg²⁺ + 2e^–

Cu²⁺ + 2e^–→ Cu

• The magnesium atoms are oxidised as they lose electrons

• The copper ions are reduced as they gain electrons