An equation that shows only those species involved in the oxidation or the reduction half of a redox (reduction-oxidation) reaction.

Example:

The redox reaction between potassium manganate VII and iron(II) sulfate may be represented by the equation:

MnO₄^- + 8H⁺ + 5Fe²⁺ Mn²⁺ + 5Fe³⁺ + 4H₂O

This shows all of the reacting species. However, if we consider only the particles being reduced then that part of the equation is:

MnO₄^- + 8H⁺ + 5e Mn²⁺ + 4H₂O

And the species being oxidised are:

Fe²⁺ Fe³⁺ + e

The whole equation is obtained by multiplying through to equalise the electrons and then adding the two half-equations.

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