At which side of the equation are electrons, \({{\text{H}}^ + }\) ions and \({{\text{H}}_{\text{2}}}{\text{O}}\) needed to complete the half-equation?

\[{\text{MnO}}_4^ - {\text{(aq)}} \to {\text{M}}{{\text{n}}^{2 + }}{\text{(aq)}}\]

A