Question

Explain the hydrides of nitrogen family under the following points:
(i) Name and formula,
(ii) Basic property,
(iii) Reducing property,
(iv) Bond angle,
(v) Melting and Boiling point

Answer 1

Hint: Follow the periodic trends in properties. Identify how each property varies as you move down the nitrogen family. On moving down the group of nitrogen families the basic character of group 15 hydrides decreases as the atomic size of the central atom increases. On moving down the group of nitrogen families the reducing character of group 15 hydrides increases.

Complete Step by step answer: Write the names and formula of the hydrides of nitrogen family as follows:
Ammonia \[{\text{N}}{{\text{H}}_3}\] , phosphine \[{\text{P}}{{\text{H}}_3}\] , Arsine \[{\text{As}}{{\text{H}}_3}\] , Stilbene \[{\text{Sb}}{{\text{H}}_3}\] and Bismuthine \[{\text{Bi}}{{\text{H}}_3}\]
Basic property:
Ammonia dissolves in water to form ammonium hydroxide. Ammonium hydroxide and ammonia are basic in nature. They are Lewis bases in nature as the lone pair of electrons on nitrogen atoms can be easily donated to a suitable Lewis acid. Like ammonia, the hydrides of other group members are also basic in nature. On moving down the group of nitrogen families the basic character of group 15 hydrides decreases as the atomic size of the central atom increases.
Reducing property increases on moving down the group due to decrease in the bond strength. Group 15 hydrides are strong reducing agents.
Bond angle decreases gradually on moving down the group. This is because with increase in the atomic size of group 15 elements, the bond-pair bond-pair repulsion decreases. Group 15 hydrides have pyramidal shape and have a lone pair of electrons on the central atom.
Melting and Boiling point of group 15 hydrides increase on moving from top to bottom in the group. Antimony and bismuth are exceptions. On moving down the group, the electropositive and metallic character increases. In the crystal lattice, the binding energy increases.

Note: In the group 15 hydride, the oxidation number of hydrogen is +1. The oxidation number of group 15 elements is -3. A Lewis base has one (or more) lone pairs of electrons on the central atom. These lone pairs of electrons can be readily donated to suitable Lewis acid. The strength of intermolecular forces determines the melting and boiling point. The strength of intermolecular forces depends on the metallic character.