Hund's Rule of Maximum Multiplicity (Electrons fill degenerate orbitals singly with parallel spins before any pairing occurs)
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Electrons fill degenerate orbitals singly with parallel spins before any pairing occurs
What each symbol means
| Symbol | What it stands for |
|---|---|
| parallel spin | All singly-occupied orbitals have same spin (all ↑ first) |
| degenerate orbitals | Orbitals with the same energy (e.g., three 2p or five 3d orbitals) |
| maximum multiplicity | Maximizes total spin S = n/2 → most stable configuration |
When to use this
Applies when filling subshells with multiple orbitals (p: 3, d: 5, f: 7). Minimizes electron-electron repulsion and maximizes exchange energy. Together with Aufbau and Pauli, determines electronic configuration.