Redox Reaction Concepts

Key Concepts

Reactions in which electrons are transferred from one species to another are known as redox reactions, or, oxidation-reduction reactions, or, electron-transfer reactions.
A redox reaction is made up of two reactions:
i) A reduction reaction in which one species gains electrons.
ii) An oxidation reaction in which one species loses electrons.
Electrons are being transferred from the species that undergoes oxidation to the species that undergoes reduction.
The species that undergoes reduction is known as the oxidant or oxidizing agent because it causes another species to be oxidized.
The species that undergoes oxidation is known as the reductant or reducing agent because it causes another species to be reduced.
In a redox reaction:
i) The oxidation state (number) of the species which gains electrons decreases.
The oxidation state (number) of the oxidizing agent (oxidant) decreases.
ii) The oxidation state (number) of the species which loses electrons increases
The oxidation number (state) of the reducing agent (reductant) increases.