Nitrogen has the electronic configuration $1{\mathrm{s}}^2,2{\mathrm{s}}^{2}2{\mathrm{p}}_{\mathrm{x}}^{1}2{\mathrm{p}}_{\mathrm{y}}^{1}2{\mathrm{p}}_{\mathrm{z}}^1\text{ and not }1{\mathrm{s}}^2,2{\mathrm{s}}^{2}2{\mathrm{p}}_{\mathrm{x}}^{2}2{\mathrm{p}}_{\mathrm{y}}^{1}2{\mathrm{p}}_{\mathrm{z}}^0.$ It was proposed by:

Follow Hund's multiplicity rule.

According to Hund’s rule:

• Before the double occupation of any orbital, every orbital in the sub level is singly occupied.
• For the maximization of total spin, all electrons in a single occupancy orbital have the same spin.