Question

Arrange the following in the increasing order of property mentioned:

NH₃, PH₃, AsH₃, SbH₃, BiH₃ (Base strength)

Arrange the following in the order of property indicated for the given set:

NH₃, PH₃, AsH₃, SbH₃, BiH₃ - increasing base strength.

Answer 1

BiH₃ < SbH₃ < PH₃ < NH₃

On moving down the group, the size of the central atom increases. This decreases the electron density on the central atom, thereby affecting the electron-donating ability of the atom. Hence, the basic strength decreases on moving down the group.