Oxidizing and Reducing 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 [CrO42-], dichromate [Cr2O72-], nitric acid [HNO3], sulfuric acid [H2SO4]).
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.