The number of ions from the following that are expected to behave as oxidising agent is :
Sn⁴⁺, Sn²⁺, Pb²⁺, Tl³⁺, Pb⁴⁺, Tl⁺

Solution

Chemistry ma’am · 3 steps

Ask which oxidation state is more stable for each element; an ion above that state is an oxidising agent.

1. Inert pair effect. Going down groups 13 and 14, the ns² pair holds on more tightly and stays out of bonding. So the lower state (group number minus 2) becomes more stable for the heavier elements.
2. How to judge. An ion that sits in the less stable higher state accepts electrons to fall to the stable state, so it is an oxidising agent. An ion in the less stable lower state gives electrons away, so it is a reducing agent.

   Ion	More stable state of the element	Behaviour
   Sn⁴⁺	+4 (inert pair effect is weak for Sn)	stable, not oxidising
   Sn²⁺	+4	reducing agent
   Pb²⁺	+2	stable
   Pb⁴⁺	+2	oxidising agent
   Tl⁺	+1	stable
   Tl³⁺	+1	oxidising agent

3. So. Only Pb⁴⁺ and Tl³⁺ readily gain electrons to reach their stable lower states, so 2 ions behave as oxidising agents.

The idea to keep. For Tl and Pb the lower state is the stable one, so their higher states oxidise. For Sn the higher state is stable, so Sn²⁺ reduces.

Answer from the NTA final answer key. Solution by PrepWiser.