Electronic Configuration

Every element of Group 15 carries the same valence-shell electronic configuration, $ns^2np^3$. The $s$ subshell is completely filled while the three $p$ orbitals each hold exactly one electron, giving a symmetrical, half-filled $p^3$ arrangement. Configurations of this kind are associated with extra stability (a smaller electron-electron repulsion and a favourable exchange energy), and this half-filled stability is a recurring theme in explaining why these elements resist further ionisation and why nitrogen in particu …