Manganese(II) oxide ($\mathrm{MnO}$)

Manganese(II) oxide is $\mathrm{MnO}$, containing manganese predominantly in oxidation state $+2$. Its ideal structure is related to the rock-salt lattice.

It differs from manganese dioxide, $\mathrm{Mn}{\mathrm{O}}_2$, where manganese is formally $+4$. Comparing the two illustrates why the oxidation-state label determines both stoichiometry and redox chemistry.