Among the hydrides $NH_3, PH_3,$ and $BiH_3$, the hydride with the highest boiling point is $X$ and the hydride with the lowest boiling point is $Y$. What are $X$ and $Y$ respectively?

Why does the reactivity of nitrogen differ from phosphorus?

Account for the following observations:
$(A)$ $AlCl_3$ is a Lewis acid.
$(B)$ Though fluorine is more electronegative than chlorine yet $BF_3$ is a weaker Lewis acid than $BCl_3$.
$(C)$ $PbO_2$ is a stronger oxidizing agent than $SnO_2$.
$(D)$ The $+1$ oxidation state of thallium is more stable than its $+3$ state.

Which of the following is the correct order of stability of hydrides of Group $15$ elements?

Phosphorus on reaction with sulphuryl chloride gives a compound $X$, which on complete hydrolysis gives $Y$. $X$ and $Y$ are respectively

How many isotopes of nitrogen gas are stable? Which are they?