(a) Give reasons for the following:
(i) Bond enthalpy of ${\mathit{F}}_2$ is lower than that of ${\mathit{C}\mathit{l}}_2$.
(ii) ${\mathit{P}\mathit{H}}_3$, has lower boiling point than ${\mathit{N}\mathit{H}}_3$.
(b) Draw the structures of the following molecules:
(i) ${\mathit{B}\mathit{r}\mathit{F}}_3$
(ii) ${\left({\mathit{H}\mathit{P}\mathit{O}}_3\right)}_3$
(iii) ${\mathit{X}\mathit{e}\mathit{F}}_4$
OR
(a) Account for the following:
(i) Helium is used in diving apparatus.
(ii) Fluorine does not exhibit positive oxidation state.
(iii) Oxygen shows catenation behaviour less than sulphur.
(b) Draw the structures of the following molecules:
(i) $\mathit{X}\mathit{e}{\mathit{F}}_2$
(ii) ${\mathit{H}}_2{\mathit{S}}_2{\mathit{O}}_8$