Though Nitrogen exhibits +5 oxidation state, it does not form pentahalide. Give reason.

$PH_{3}$ has a lower boiling point than $NH_{3}$. Why?

Why are pentahalides more covalent than trihalides?

Why is $BiH_{3}$ the strongest reducing agent amongst all the hydrides of Group 15 elements?

Write the reaction of thermal decomposition of sodium azide.