In highest oxidation states, the transition metals show acidic character

$$\mathrm{Mn}^{3+}$$ and $$\mathrm{CO}^{3+}$$ are oxidising agents in aqueous solution

Metals in highest oxidation states are more stable in oxide than in fluorides

All elements of $$3 d$$ series exhibit variable oxidation states

malachite

cuprite

azurite

chalcopyrite

$\mathrm{SiO}_2$

MgO

$\mathrm{SO}_2(\mathrm{~s})$

$\mathrm{CrO}_2$

+2

+3

+4

+5