Why scientists care
Hund’s rule describes the lowest-energy filling pattern within a set of degenerate orbitals: electrons occupy different orbitals with parallel spins before pairing, in the usual atomic model.
It helps explain ground-state electron configurations and magnetic behaviour, but it belongs to a broader quantum-mechanical energy picture.
A concrete example
In equal-energy orbitals, electrons occupy separate orbitals before pairing, which helps explain atomic magnetic behaviour.
Try to notice
Science becomes memorable when a definition is connected to something measurable or observable.