Question

How do the oxides of the transition elements in lower oxidation states differ from those in higher oxidation states in the nature of metal-oxygen bonding and why?

Answer 1

1. Oxides of transition metals in lower oxidation states mostly exhibit ionic bonding with oxygen, making them generally basic.
2. In higher oxidation states, the metal-oxygen bonds are predominantly covalent because the metal uses (n − 1)d electrons in addition to ns electrons for bonding.
3. This leads to oxides in higher oxidation states being acidic in nature.
4. The involvement of d-electrons in higher states provides stronger, more covalent metal-oxygen bonds, while lower states mostly lose only s-electrons and form ionic bonds.
5. Intermediate oxidation states often yield amphoteric oxides, showing mixed bonding character.

This is because in lower states metals use mainly ns electrons forming ionic bonds, but in higher states, both ns and (n − 1)d electrons participate, creating covalent bonds with oxygen.