Question

To what extent do the electronic configuration decide the stability of oxidation states in the first series of transition elements ? Illustrate your answer 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. For example, in the first transition series, electronic configuration of Mn `(Z= 25)` is `[Ar]3d^(5) 4s^(2)`. It shows oxidation states `+2` to `+7` but Mn (II) is most stable becasue it has the half - filled configuration `[Ar] 3d^(5)`
Similarly `Sc^(3+)` and `Zn^(2+)` are more stable as illustration below `:`
`. _(21) Sc = [Ar] 3d^(1) 4s^(2) , Sc^(3+) = [Ar] , i.e., `noble gas configuration
`._(30)Zn = [Ar] 3d^(10) 4s^(2) , Zn^(2+) = [ Ar] 3d^(10) , `i.e., completely filled configuration