In nitrogen's ground-state orbital diagram, the three 2p electrons occupy three separate orbitals with parallel spins. Which principle requires this arrangement?

Core Concept

Hund's rule states that electrons fill degenerate orbitals singly and with parallel spins before any orbital pairs up. Spreading the three 2p electrons apart minimizes repulsion for a given filling. Nitrogen's half-filled 2p subshell is the textbook consequence.