Compound ${\mathrm{SO}}_3$ has $\mathrm{x}$ bond pairs and $\mathrm{y}$ lone pairs. Calculate the value of $\mathrm{x}+\mathrm{y}.$

Find the number of molecules having two lone pairs on the central atom.

(i) ${\mathrm{I}}_3^{+}$ (ii) ${\mathrm{XeF}}_2$ (iii) ${\mathrm{XeF}}_4$ (iv) ${\mathrm{H}}_2\mathrm{O}$ (v) ${{\mathrm{NH}}_2}^{-}$ (vi) ${\mathrm{H}}_2\mathrm{S}$ (vii) ${\mathrm{H}}_2{\mathrm{SO}}_4$ (Viii) ${\mathrm{NF}}_3$

Which of the following species are hypervalent?

$1$. ${\mathrm{ClO}}_4^{-}$

$2$. ${\mathrm{BF}}_3$

$3$. ${\mathrm{SO}}_4^{2-}$

$4$. ${\mathrm{CO}}_3^{2-}$