Question

Give an example and suggest a reason for the following feature of the transition metal chemistry:

The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.

Account for the following:

The lowest oxide of transition metal is basic whereas the highest oxide is amphoteric or acidic.

Account for the following:

The lowest oxide of transition metal is basic, and the highest is acidic.

Answer 1

The lowest oxide has the lowest oxidation state of the transition metal. Hence, the oxide is basic and tends to react with acids to get oxidised to attain a higher oxidation state. Whereas the highest oxides are formed in higher oxidation states. As a result, these oxides are amphoteric acidic. For example, MnO is basic, whereas Mn₂O₇ is acidic.

Answer 2

In the case of a lower oxide of a transition metal, the metal atom has some electrons present in the valence shell of the metal atom that are not involved in bonding. As a result, it can donate electrons and act as a base, whereas in the higher oxide of a transition metal, the metal atom lacks an electron in the valence shell to donate. As a result, it can accept electrons and behave as an acid.