Question

Which of the following is incorrect about group $15$ hydrides (from ammonia to bismuth)?

• A. Their thermal stability gradually increases
• B. Their basic nature gradually decrease
• C. The electron pair donating nature gradually decreases
• D. The bond energies gradually increases

Answer 1

Answer: (A), (D)

The bond energies gradually increases

As we go down the group, the size of atom increases, lone pair occupies more volume and so electron pair donating nature gradually decreases. Therefore, the basic nature of hydrides decreases down the group. As the size increases down the group, bond distance between element and $H$-atom increases and hence bond energy decreases. So thermal stability also decreases as we move from top to bottom.
Hence, option (a),(b) and(d) are the correct answers.