Ø  Reactivity Towards Hydrogen: All elements of group 15 react with Hydrogen to form Hydrides of the type EH3 (where E = N, P, As, Sb or Bi). They belong to sp3 hybridisation. The stability of hydrides decreases down the group due to decrease in bond dissociation energy down the group. NH3 > PH3 > AsH3 > SbH3 > BiH3.

·       Bond angles: NH3 > PH3 > AsH3 > SbH3 > BiH3
Electronegativity of N is highest. Therefore, the lone pairs will be towards nitrogen and hence more repulsion between bond pairs. Therefore, bond angle is the highest. After nitrogen, the electronegativity decreases down the group.

·       Bond Dissociation Enthalpy: NH3 > PH3 > AsH3 > SbH3 > BiH3
Bond dissociation enthalpy of E – H decreases from NH3 to BiH3 due to increase in size and E – H bond length. So, the thermal stability also decreases from NH3 to BiH3.

·       Boiling Point: PH3 < AsH3 < NH3 < SbH3 < BiH3
Boiling point increases with increase in size due to increase in extent of van-der Waal’s forces.
Boiling point of NH3 is more because of hydrogen bonding.


·       Basic Nature: Basic nature depends on the availability of lone pair of electrons. NH3 > PH3 > AsH3 > SbH3 > BiH3.
Size of central atom increases and the availability of lp of e− for protonation decreases. So, the basic nature decreases.

·       Reducing Nature: NH3 < PH3 < AsH3 < SbH3 < BiH3
Size of central atom increases and the thermal stability decreases. Ease of availability of hydrogen increases.

Ammonia forms hydrogen bonding with water molecules, therefore it is soluble in water, while other hydrides are insoluble in water.