Oxidation and Reduction

The process in which an atom or ion looses one or more electron to the other is called oxidation and the process in which an atom or ion gains one or more electron is termed as reduction.

For example,

Na → Na⁺ + e^– (loss of e^– by Na; oxidation)

Cl + e^– → Cl^– (gain of e^– by Cl; reduction)

Sodium undergoes oxidation and chlorine undergoes reduction. Here, sodium helps chlorine to undergo reduction and therefore it is called a reducing agent or reductant. A reductant is a species in a chemical reaction which looses its electron to another reactant.

Chlorine is an oxidizing agent or oxidant. An oxidant is a species which accepts electrons in a chemical reaction.

Oxidation and reduction processes do not take place independently but occur simultaneously and are called oxidation-reduction reaction or redox reactions. A redox reaction is a sum of oxidation and reduction half reactions in a chemical reaction.