A chemical reaction in which oxidation and reduction take place simultaneously is called a redox reaction.
Oxidation: I. The addition of oxygen is called oxidation.
Ex: 2 Mg + O2→ 2 MgO
II. The addition of electronegative elements is oxidation.
Ex: Mg + F2→MgF2
III. The removal of Hydrogen is also oxidation.
IV. The removal of electropositive elements is called oxidation.
Ex: 2 K4[Fe(CN)6]+H2O2→2 K3[Fe(CN)6]+2 KOH
Reduction: I. The removal of oxygen is called reduction.
II. The removal of electronegative elements is reduction.
III. The addition of Hydrogen is also reduction.
IV. The addition of electropositive elements is reduction.