Question

Among the hydrides of group 15, predict the hydride having highest thermal stability.

Answer 1

1. Among the hydrides of group 15 elements (NH₃, PH₃, AsH₃, SbH₃, BiH₃), ammonia (NH₃) has the highest thermal stability.
2. Thermal stability decreases down the group due to increasing bond length and decreasing M-H bond energy.
3. NH₃ also forms hydrogen bonds, which add to its stability.
4. The thermal stability order is, NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃.

Thus, ammonia (NH₃) is the most thermally stable hydride in group 15.