Hund's rule
How are nitrogen's three 2p electrons arranged in its ground state?
Answer A: explanation for every choice
A
Correct. Hund's rule: electrons fill degenerate orbitals singly with parallel spins before pairing.
B
Pairing before every orbital has one electron raises the energy.
C
An orbital holds at most two electrons, by the Pauli exclusion principle.
D
Single electrons in degenerate orbitals have parallel spins in the ground state.
TakeawayHund's rule: spread out singly, with parallel spins, before pairing.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp98.