(a) Account for the following :
(i) `PCl_(5)` is more covalent than `PCl_(3)`.
(ii) Iron on reaction with HCl forms `FeCl_(2)` and not `FeCl_(3)`.
(b) Draw sturcture of `XeO_(3)`.

Explanation

(i) It is difficult to lose all the three electrons to form `p^(3+)` or even more difficult to lose all the five valence electrons to form `p^(5+)` ions. Therefore, higher elements have no tendency to form ionic compounds. Instead they form covalent compounds by sharing of electrons.
Since elements in the +5 oxidation state have less tendency to lose electrons than in the +3 oxidation state. Hence, elements in the +5 oxidation state have more tendency to share electrons than in the +3 oxidation state. Thus, elements in the +5 oxidation state are more covalent than in the +3 oxidation state.
(ii) Fe reacts with HCl to form `FeCl_(2)` and `H_(2)`,
`Fe + 2HCl rarr FeCl_(2) + H_(2)`
`H_(2)` thus liberated prevents the oxidation of `FeCl_(2)` to `FeCl_(3)`.
(b)