The number of ions from the following that are expected to behave as oxidising agent is : $$Sn^{4+}, Sn^{2+}, Pb^{2+}, Tl^{3+}, Pb^{4+}, Tl^{+}$$

We need to identify how many ions from $$Sn^{4+}, Sn^{2+}, Pb^{2+}, Tl^{3+}, Pb^{4+}, Tl^{+}$$ behave as oxidising agents.

Key Concept: Inert Pair Effect and Oxidising Behaviour

An oxidising agent is a species that readily accepts electrons (gets reduced). Due to the inert pair effect, the higher oxidation states of heavier p-block elements are less stable, making them strong oxidising agents as they tend to get reduced to the lower oxidation state.

Analysis of each ion:

- $$Sn^{4+}$$: Tin in +4 state. While $$Sn^{2+}$$ is more stable for heavier members, $$Sn^{4+}$$ is actually quite stable for tin (Period 5), so it is not a particularly strong oxidising agent.

- $$Sn^{2+}$$: This is a reducing agent (gets oxidised to $$Sn^{4+}$$), not an oxidising agent.

- $$Pb^{2+}$$: Lead in +2 state is the more stable oxidation state of lead. It is not an oxidising agent in this context.

- $$Tl^{3+}$$: Thallium in +3 state is unstable due to the strong inert pair effect in Period 6. $$Tl^{3+}$$ readily gets reduced to $$Tl^{+}$$, making it a strong oxidising agent.

- $$Pb^{4+}$$: Lead in +4 state is unstable due to the inert pair effect. $$Pb^{4+}$$ readily gets reduced to $$Pb^{2+}$$ (e.g., $$PbO_2$$ is a strong oxidising agent). Strong oxidising agent.

- $$Tl^{+}$$: This is the more stable state of thallium. It is not an oxidising agent.

The ions that act as oxidising agents are $$Tl^{3+}$$ and $$Pb^{4+}$$ -- a total of 2 ions.

The correct answer is Option 2: 2.