Amongest the elements of group-14, the oxidising power of the tetravalent species increases in the order.

Due to inert pair effect , the stability of '+4' oxidation state decreases & '+2' state increases down the group  The order of stability is ,   Ge+4 > Sn+4 > Pb+4    The order of oxidizing power is ,  Ge+4 < Sn+4 < Pb+4 Hence in '+4' oxidation state lead acts as a good oxidizing agent and it self reduces to  stable Pb+2In case of ' Ge & Sn '  +4 state is more stable than +2