Reducing agent

A reducing agent (also called a reductant or reducer) is the element or a compound in a redox (reduction-oxidation) reaction (see electrochemistry) that reduces another species. In doing so, it becomes oxidized, and is therefore the electron donor in the redox. For example consider the following reaction:

The reducing agent in this reaction is magnesium. Magnesium donated its two valence electrons, has become an ion, and allows itself as well as oxygen to become stable.