Half reaction 1: 2Fe° → Fe₂³⁺ + 6e⁻ /×2.
4Fe° → 2Fe₂³⁺ + 12e⁻.
Iron is oxidized from neutral charge (0) to oxidation number +3, one iron lose three electrons, two irons lose six electrons and four irons twelve electrons.
Half reaction 2: 12e⁻ + 3O₂ → 2O₃²⁻
Oxygen is reduced from neutral chage to oxidation number -2, one oxygen gain two electrons, six oxygens gain twelve electrons.
Balanced chemical reaction: 4Fe + 3O₂ → 2Fe₂O₃.
