The inability of ns2 electrons of the valence shell to participate in bonding on moving down the group in heavier p−block elements is called inert pair effect.
As a result,Pb(II)is more stable than Pb(IV)
Sn(IV) is more stable than Sn(II)
∴ Pb(IV) is easily reduced to Pb(II).
∴ Pb(IV) is an oxidizing agent.
Sn(II) is easily oxidized to Sn(IV)
∴ Sn(II)is reducing agent.