Assign a reason for each of the following statements :
(i) Ammonia is a stronger base than phosphine.
(ii) Sulphur in vapour state exhibits a paramagnetic behaviour.

Explanation

(i) Both `NH_(3)` and `PH_(3)` have a lone pair of electrons on the central atom. Hence, they act as Lewis bases. When `NH_(3)`or `PH_(3)` accepts a proton to form `NH_(4)^(+)PH_(4)^(+)`, an additional `N-H` or `P-H` bond is formed.
`H_(3)N : +H^(-) to NH_(4)^(+)`
`H_(3)P : +H^(-) to PH_(4)^(+)`
Now, because of the smaller size and the unavailability of d-orbitals in N, the lone pair on N is less delocalised than the lone pair present on P. Thus the N-H bond is much stronger than the `P-H` bond. As a result, the ability of `NH_(3)` to accept a proton is much more than that of `PH_(3)`. Therefore, `NH_(3)` is a stronger base than `PH_(3)`.
(ii) In vapour state, sulphur exists as `S_(2)` molecule. `S_(2)` molecule, like `O_(2)`, has two unpaired electrons in the anti-bonding `n*`orbitals. Hence, like `O_(2)`,it exhibits paramagnetism.