The exhibition of various oxidation states

Question:
The exhibition of various oxidation states by an element is also related to the outer orbital electronic configuration of its atom. Atom(s) having which of the following outermost electronic configurations will exhibit more than one oxidation state in its compounds.

(i) 3s1

(ii) 3d1 4s2

(iii) 3d2 4s2

(iv) 3s2 3p3

Solution:

Option (iii) 3d2 4s2 and (iv) 3s2 3p3 are the answers.