TeX source:

\begin{align}\overset{+7\,\, -2}{2MnO_{4}^{-}}+\overset{+4\,-2}{5SO_{2}}+\overset{+1\,\,-2}{6H_{2}O}\rightarrow \\ \overset{+6\,-2\,\,\,\,\,}{5SO_{4}^{2-}}+\overset{+2\,\,\,\,\,}{2Mn^{2+}}+\overset{+1\,-2\,\,\,\,}{4H_{3}O^{+}}\end{align}