If the electronic configuration of nitrogen has $1{\text{s}}^7$. It would have energy lower than that of the normal ground state configuration ${\text{1s}}^{\text{2}}{\text{\hspace{0.17em}2s}}^{\text{2}}{\text{\hspace{0.17em}2p}}^{\text{3}}$ because the electrons would be closer to the nucleus.  Yet $1{\text{s}}^7$ is not observed because it violates