Generally, oxides are basic when the metal is in lower oxidation state and acidic, when in higher oxidation state. The oxides are generally amphoteric, when the metal is in intermediate oxidation state, e.g., MnO (basic), $\mathrm{M}{\mathrm{n}}_2{\mathrm{O}}_3$ (amphoteric), $\mathrm{M}\mathrm{n}{\mathrm{O}}_2$ (amphoteric) and $\mathrm{M}{\mathrm{n}}_2{\mathrm{O}}_7$ (acidic).