Discuss the trends in chemical reactivity of group $15$ elements.

(N/A) The ionisation enthalpies of group-$15$ elements are much higher than corresponding group-$14$ elements due to increased nuclear charge,reduced atomic radii,and stable half-filled $ns^2np^3$ electronic configuration,resulting in a very low tendency to lose electrons.
Down the group,there is a decrease in the ionisation enthalpy due to an increase in atomic size,which decreases the force of attraction on electrons by the nucleus. The order of successive ionisation enthalpies is $\Delta_{i}H_{1} < \Delta_{i}H_{2} < \Delta_{i}H_{3}$.
Nitrogen is the most electronegative element in group-$15$. Down the group,electronegativity decreases with an increase in atomic size. However,amongst the heavier elements,the difference is not very pronounced.