Question

The least stable hydride of $15^{th}$ group elements is

• A. $ N{{H}_{3}} $
• B. $ P{{H}_{3}} $
• C. $ As{{H}_{3}} $
• D. $ Sb{{H}_{3}} $
• E. $ Bi{{H}_{3}} $

Answer 1

Answer: (E)

Thermal stability of hydrides of N family decreases gradually from $ N{{H}_{3}} $ to $ Bi{{H}_{3}} $ due to increase in $ MH $ bond strength down the group on account of increase in size of central atom.
$ N{{H}_{3}} > P{{H}_{3}} > As{{H}_{3}} > Sb{{H}_{3}} > Bi{{H}_{3}} $
Decomposit $ 1300{}^\circ C\text{ }440{}^\circ C\text{ }280{}^\circ C~150{}^\circ C $
Room ion temp. : temp.