Question

Why Sn2+ is a reducing agent but Pb 2 + is not

Answer 1

Inert pair effect is more dominant in Pb than in Sn.

Hence Pb is more stable in Pb2+ and Sn in Sn4+.

So Sn2+ is a reducing agent (oxidises itself to Sn4+ hence becoming stable) while Pb2+ is already stable so it neither undergoes oxidation nor reduction.