4.9 Oxidation–Reduction Reactions

Oxidation is loss of electrons; reduction is gain (OIL RIG). The species oxidized is the reducing agent.

Assign oxidation numbers: elements 0, O usually −2, H usually +1, sum = charge.

Balance redox in acid: half-reactions → balance atoms → O with H₂O → H with H⁺ → charge with e⁻ → equalize e⁻.

Worked example: In MnO₄⁻, Mn = +7.