${\mathrm{AlCl}}_3$ is compound whereas ${\mathrm{PCl}}_5$ is a hypervalent compound in terms of octet rule.(electron deficient/electron rich)

Write the Lewis dot structures of the following:

${\mathrm{H}}_2{\mathrm{SO}}_4$

A chemical compound has the following Lewis notation:

What is the valency of element $\mathrm{Y}$?

A chemical compound has the following Lewis notation:

To which groups the elements $\mathrm{X}$ and $\mathrm{Y}$ belong?