Hund's Rule — Definition, Formula, Properties & Uses | AllChemicals | AllChemicals

Also Known As	Hund's rule of maximum multiplicity, maximum multiplicity rule, orbital filling rule

What is Hund's Rule?

Hund's Rule (Hund's Rule of Maximum Multiplicity) states that when electrons occupy orbitals of equal energy (degenerate orbitals), each orbital is occupied by one electron before any orbital receives a second electron. Furthermore, all electrons in singly occupied orbitals have the same spin (parallel spins). This minimizes electron-electron repulsion and results in the most stable configuration.

Properties & Characteristics

Applies to degenerate orbitals (same subshell, same energy). One electron per orbital first — parallel spins. Example: carbon 2p: ↑_ ↑_ __ (not ↑↓ __ __ ). Maximizes spin multiplicity (2S+1). Results in maximum number of unpaired electrons. Parallel spins have lower energy due to exchange interaction.

Uses & Applications

Predicting electron configurations of atoms and ions. Explaining paramagnetism (unpaired electrons). Understanding spectroscopic states and term symbols. Explaining stability of half-filled subshells (e.g., Cr: [Ar]3d⁵4s¹). Teaching atomic structure and the periodic table. Quantum chemistry calculations.

Safety Information

Theoretical rule — no direct safety concerns.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Hund's Rule

Index All "H" terms

Synonyms Hund's rule of maximum multiplicity, maximum multiplicity rule, orbital filling rule

Frequently Asked Questions

What is Hund's Rule?

Hund's Rule (Hund's Rule of Maximum Multiplicity) states that when electrons occupy orbitals of equal energy (degenerate orbitals), each orbital is occupied by one electron before any orbital receives a second electron. Furthermore, all electrons in singly occupied orbitals have the same spin (parallel spins). This minimizes electron-electron repulsion and results in the most stable configuration.

What is Hund's Rule used for?

Is Hund's Rule hazardous?

More "H" Terms

Haber Process N₂ + 3H₂ ⇌ 2NH₃ | ΔH = −92 kJ/mol Hafnium Hf Half Cell Half Life Half-Cell E = E° − (RT/nF)lnQ Half-Life A(t) = A₀e^(−λt); t½ = ln2/λ Half-Reaction Halide X⁻ (e.g., F⁻, Cl⁻, Br⁻, I⁻) Halogen F₂, Cl₂, Br₂, I₂, At; Group 17; ns²np⁵ valence configuration Halogenation C-X + Cl₂/Br₂ (hv or AlCl₃) → C-X(halogen); EAS or radical pathway Halogens Hard Acid Hard acid: small, highly charged, low polarisability (e.g., H⁺, Mg²⁺, Al³⁺)

View all "H" terms →