Formation of oxides of d-block elements
Transition metals form oxides on reaction with oxygen at elevated temperature. Transition metal form oxide in oxidation state of + 1 (in Ag2O) to + 7 (Mn2O7) to + 8 (in OsO4). As the oxidation number increases in case of same elements:
- The covalent character of oxides increases.
- The acidic strength of the oxides increases.
- The oxidizing power of oxides increases.
For example, Cr2O3 is amphoteric while CrO is basic and CrO3 is acidic.