All the members form volatile hydrides of the type AH₃ . All hydrides are pyramidal in shape. The bond angle decreases on moving down the group due to decrease in bond pair–bond pair repulsion.

The decreasing order of basic strength of hydrides is as follows :

NH₃ > PH₃ AsH₃ > SbH₃ > BiH₃ .

The increasing order of boiling points is as follows :

PH₃ < AsH₃ < NH₃ < SbH₃ .

NH₃ is thermally most stable and BiH₃ is least stable. This is because in NH₃ , N – H covalent bond is the strongest due to small size of N atom. Hence, the decomposition temperature of NH₃ will be the highest. The increasing order of reducing character is as follows, NH₃ < PH₃ AsH₃ < SbH₃ < BiH₃ .