Half Equation - GCSE Chemistry Definition

A half equation is a way of showing one part of a chemical reaction, specifically the part where electrons are either gained or lost. In chemistry, reactions often involve the transfer of electrons, and each half equation focuses on one of these parts, either the loss (oxidation) or the gain (reduction) of electrons. This is important for understanding redox reactions, which are reactions involving both oxidation and reduction processes. For example, if you have a metal atom like sodium, turning into a positive ion by losing electrons, you would write a half equation to show just this change, including the electrons that are lost as shown : Na → Na⁺ + e⁻. Understanding half equations helps students balance chemical equations and see what happens at the atomic level during a chemical change.