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

Assign a reason for each of the following statements : (i) Ammonia is

1.	Assign a reason for each of the following statements : (i) Ammonia is a stronger bass than pjhosphine. (ii) Sulpher in vapour state exhibits a paramagnetic behaviour :
Answer» Solution :(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.