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

When metal X is treated with sodium hydroxide, a white precipitate (A) is obtained, which is soluble in excess of $\mathrm{NaOH}$ to give soluble complex (B). Compound (A) is soluble in dilute $\mathrm{HCl}$ to form compound (C). The compound (A) when heated strongly gives (D), which is used to extract metal. Identify (X), (A), (B), (C) and (D). Write suitable equations to support their identities.

What do you understand by the term inert pair effect?

A certain salt $\mathrm{X}$, gives the following results.
(i) Its aqueous solution is alkaline to litmus.
(ii) It swells up to a glassy material $\mathrm{Y}$on strong heating
(iii)When conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$ is added to a hot solution of $\mathrm{X}$, white crystal of an acid $\mathrm{Z}$ separates out. 

Write equations for all the above and identify $\mathrm{X}, \mathrm{Y} \& \mathrm{Z}$ .