Chemistry - Complete P-block Question with Solution | TestHub

The size of halogen increases from $\mathrm{F}$ to $\mathrm{I}$. The $\mathrm{N}-\mathrm{F}$ bond is stronger than other $\mathrm{N}-\mathrm{X}$ bonds due to the high electronegativity of fluorine. Larger the size of the halogen, less is the stability of nitrogen halide:

The stability order is ${\mathrm{NF}}_3>{\mathrm{NCl}}_3>{\mathrm{NBr}}_3>{\mathrm{NI}}_3$.