Question

Compound which has the highest thermal stability is?

• A. $As{H}_3$
• B. $P{H}_3$
• C. $N{H}_3$
• D. $Sb{H}_3$

Answer 1

The correct option is C $N{H}_3$

Down the group in periodic table the thermal stability of hydride decrease because the size of the central atom increase down the group. Thus the overlapping between orbitals of cental atom and hydrogen will not be efficient, making the bond weaker. Hence the stability of the hydrides decrease and can be decomposed easily by heat.
Therefore $N{H}_3$ has high thermal stability.