Oxidizing and Reducing Agents

Oxidizing Agents

An oxidizing agent is a substance that oxidizes another substance. In doing so, it becomes reduced.

Relatively strong oxidizing agents tend to have a large affinity for electrons. Such agents are:


very electronegative (e.g. F₂, Cl₂, O₂, O₃)
or have high oxidation states (e.g. permanganate [MnO₄^-], chromate [CrO₄^2-], dichromate [Cr₂O₇^2-], nitric acid [HNO₃], sulfuric acid [H₂SO₄]).

Reducing Agents

A reducing agent is a substance that reduces another substance. In doing so, it becomes oxidized.

Relatively strong reducing agents are able to lose electrons easily: they have small ionization energies and low electronegativities (e.g. metals such as sodium, magnesium, aluminum, zinc; metal hydrides such as NaH, CaH₂).

Relative Strengths of Oxidizing and Reducing Agents

A measure of how easily a substance is reduced is given by its standard state reduction potential, E⁰. The higher the E⁰, the more easily it is reduced, and the stronger an oxidizing agent it is. Conversely, the more negative the E⁰, the more easily it is oxidized, and the stronger a reducing agent it is.