Elements of Group $16$ generally show lower value of first ionisation enthalpy compared to the corresponding periods of Group $15$. Why?

(N/A) The electronic configuration of Group $15$ elements is $ns^2 np^3$,which represents a half-filled $p$-orbital configuration.
This configuration is extra stable due to exchange energy and symmetry.
In contrast,Group $16$ elements have an electronic configuration of $ns^2 np^4$.
Removing an electron from the stable half-filled $p$-orbital of Group $15$ requires more energy than removing an electron from the $np^4$ configuration of Group $16$ elements.
Therefore,Group $16$ elements have lower first ionisation enthalpy values compared to Group $15$ elements.