Question
Explain why NH3 is basic while BiH3 only feebly basic.
Solution
Nitrogen atom has the smallest size and a very high electron density aroun the nitrogen. Therefore, its electron releasing tendency or the basic strength is the maximum. Down the group, there is a gradual increase in atomic size and decrease in the electron density on the central atom. Consequently, the electron releasing tendency or basic strengths of the hydrides decrease in the order as given below
NH3 > PH3 > AsH3 > Sb H3 > BiH3
Therefore, NH3 is basic while BiH3 is only feebly basic.
