ion half equation

Equation that describes the reactions occurring at the electrodes of a chemical cell or in electrolysis. It indicates which ion is losing electrons (oxidation) or gaining electrons (reduction).

Examples are given from the electrolysis of dilute hydrochloric acid (HCl):

2Cl− − 2e− → Cl2 (positive electrode)

2H+ + 2e− → H2 (negative electrode)