Question

In some of the reactions thallium resembles aluminium, whereas in others it resembles with group I metals. Support this statement by giving some evidences.

Answer 1

Thallium is a group 13 element with common oxidation states +1 and +3.
Due to inert pair effect +1 oxidation state in Tl is more stable than +3 oxidation state. Al shows +3 oxidation state and alkali metals shows +1 oxidation state. Thus, thallium resembles both Al, and alkali metals.
Like Al, Tl forms compounds such as $TlC{l}_3$ and $T{l}_2{O}_3$ and like alkali metals, Tl forms compounds such as $TlCl$ and $T{l}_{2}O.$