Question

To what extent do the electronic configurations decide the stability of oxidation states in the first series of transition elements? Illustrate with example.

Answer 1

In a transition series, the oxidation states which lead to noble gas or exactly half-filled or completely filled d-orbitals are more stable.

eg. In the first transition series, electronic configuration of Mn (Z = 25) is [Ar] 3d⁵ 4s² . It shows oxidation states +2 to +7, but Mn (II) is most stable because it has the half-filled configuration [Ar] 3d⁵ .

Similarly, Sc³⁺ and Zn²⁺ are more stable as illustrated below:

Sc = [Ar] 3d¹ 4s² , Sc³⁺ = [Ar] i.e., noble gas configuration.

Zn = [Ar] 3d¹⁰ 4s² , Zn2+ = [Ar] 3d¹⁰ i.e., completely filled configuration.