Write a note on oxides and oxoanions of transition elements.

(N/A) The ability of oxygen to stabilize the high oxidation states of metals is greater than that of fluorine because oxygen can form multiple bonds with the metal.
Metal oxides in lower oxidation states are basic,while those in the highest oxidation states are acidic. Metal oxides with intermediate oxidation states are amphoteric.
For example: $Mn_{2}O_{7}$ is acidic,$MnO$ is basic,while $Mn_{3}O_{4}$,$Mn_{2}O_{3}$,and $MnO_{2}$ are amphoteric. Similarly,$CrO$ is basic,but $Cr_{2}O_{3}$ is amphoteric.
Oxides are generally formed by the reaction of metals with oxygen at high temperatures. Scandium forms only one oxide,$Sc_{2}O_{3}$,in which it is in its highest oxidation state of $(+3)$. The oxidation state often coincides with the group number,which is observed up to manganese (e.g.,$Mn_{2}O_{7}$). Beyond manganese,except for iron,no other element forms an oxide of the type $M_{2}O_{3}$ (e.g.,$Fe_{2}O_{3}$).
Although ferrates $(FeO_{4}^{2-})$ are formed in an alkaline medium,they readily decompose to give $Fe_{2}O_{3}$ and $O_{2}$. Besides oxides,oxocations stabilize $V^{+5}$ as $VO_{2}^{+}$,$V^{4+}$ as $VO^{2+}$,and $Ti^{4+}$ as $TiO^{2+}$. $V_{2}O_{5}$ is amphoteric,though mainly acidic,and it gives $VO_{4}^{3-}$ as well as $VO^{2+}$ salts. In vanadium,there is a gradual change from the basic $V_{2}O_{3}$ to less basic $V_{2}O_{4}$ to amphoteric $V_{2}O_{5}$. $V_{2}O_{4}$ dissolves in acid to give $VO^{2+}$ salts,while $V_{2}O_{5}$ when dissolved in alkali gives $VO_{4}^{3-}$ and in acids gives $VO_{2}^{+}$ ions.
Oxides with metals in low oxidation states have the ability to get oxidized and are therefore basic,while oxides with high oxidation states have a tendency to get reduced and are therefore acidic in nature. The ionic character of metal oxides decreases with an increase in the oxidation number of the metal. For example,$Mn_{2}O_{7}$ is a covalent green oil,while $CrO_{3}$ and $V_{2}O_{5}$ have low melting points.