Give examples and suggest reason for the following features of the transition metals Chemistry.
(ii). A transition metal exhibits highest oxidation state in oxides and fluorides.
(iii). The highest oxidation state is exhibited in oxoanions of a metal.

Explanation

(a). The lower oxide of transition metal is basic because the metal atom has low oxidation state whereas highest is acidic due to highest oxidation state. For example, MnO is basic whereas `Mn_2O_7` is acidic.
(b). A transition metal exhibits higher oxidation states in oxides and fluorides because oxygen and fluorine are highly electronegative elements, small in size (and strongest oxidising agents). For example, osmium shows an oxidation states of `+6` in `OsF_6` and vanadium shows an oxidation states of `+5` in `V_2O_5`.
(c). Oxometal anions have highest oxidation state, e.g., Cr in `Cr_2O_7^(2-)` has an oxidation state of `+6` whereas Mn in `MnO_4^(ɵ)` has an oxidation state of `+7`. This is again due to the combination of the metal with oxygen, which is highly electronegative and oxidising element.