Question

Arrange the following in the increasing order of their basic character:
$N{H}_3,P{H}_3,AS{H}_3,Sb{H}_3,Bi{H}_3$

Answer 1

The hydrides of nitrogen family contain one lone pair on the central atom. As we move down the group the size of the central atom increases thereby their orbital become more diffused, hence the nucleophilicity of the lone pair is less dense over the bigger atoms thereby decreasing the basicity. So, the increasing order of their basic character is,

$Bi{H}_3<Sb{H}_3<As{H}_3<P{H}_3<N{H}_3$