OXIDATION AND REDUCTION

Oxidation is a process that involves an increase in oxidation state = loss of electrons.

Reduction is a decrease in oxidation state = gain of electrons

Examples:

2 Na + Cl₂ → 2 NaCl

Na is oxidized (reducing agent)
Cl₂ is reduced (oxidizing agent)

Figure
Combustion of methane in oxygen, producing carbon dioxide and water, and releasing energy
Carbon is oxidized
Oxygen is reduced

In biological systems:
Carbon may be oxidized by oxidizing agents other than O₂ in stepwise reactions, and the energy is gradually released in smaller amounts.