alleryHund's rule of maximum multiplicity says that in a set of degenerate orbitals:
APair electrons first, then occupy empty orbitals
BSingly fill orbitals with parallel spins first
CLower-energy orbitals are always filled first
DElectrons prefer opposite spins from the start
Answer & Solution
Correct answer: B. Singly fill orbitals with parallel spins first
1. Hund's rule: for degenerate orbitals (same energy), electrons occupy each orbital singly with parallel spins BEFORE any pairing.
2. Minimises electron-electron repulsion → lower total energy.
3. So 2p³ in nitrogen has three unpaired electrons all spin-aligned.
_Source: syllabus Chem Ch 2 §2.6 Hund's Rule_
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