Redox Reaction in Terms of Transfer of Electron by Whatsapp Cikgu Kwee now! Oxidation and Reduction in Terms of Electron Transfer Oxidation occurs when a reactant loses electron.Reduction occurs when a reactant gain of electron.Example:CuO + Mg → Cu + MgOIn this reaction,copper (II) ion in copper(II) oxide gains 2 electrons to form copper metal.Half equation:Cu2+ + 2e → CuThis is a reduction process.Magnesium metal loses 2 electrons to form magnesium ions in magnesium oxide.Half equation:Mg → Mg2+ + 2eThis is a oxidation process.SummaryMagnesium is oxidised because it loses2 electrons to form magnesium ion, Mg2+.Copper(II) oxide is reduced because copper(II) ion gains 2 electrons to form copper metal, Cu. Whatsapp Cikgu Kwee now!