Half-Reaction
An equation showing either the oxidation or the reduction part of a redox process, including the electrons transferred.
Formula / equation
Ox + n e⁻ ⇌ Red
Unit
Dimensionless
In depth
Half-reactions cannot occur alone but are enormously useful for bookkeeping: they are balanced separately for atoms and charge, then combined so the electrons cancel. Each half-reaction corresponds to one electrode of a cell and has its own standard potential.
Examples in the real world
MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O, the reduction half at the cathode of a permanganate titration.