Hund's Rule
Version 1.0.0 · Updated 2026-07-28
CORE DEFINITION
Hund's rules (also spelled Hundt's rules) are rules in atomic physics concerning the energy level ordering of electron configurations in L-S coupling. In 1925, German physicist Friedrich Hund proposed the first two rules regarding the total spin quantum number S and the total orbital angular momentum quantum number L. In 1927, a third rule concerning the total angular momentum quantum number J was added, expanding the set to three rules. (The Hund's rule that appears in middle school textbooks is often the first rule, also known as Hund's rule of maximum multiplicity.) He pointed out that for a set of atomic states, the one with the maximum spin multiplicity 2S+1 has the lowest energy. It can also be expressed as S...
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Hund's rules are a set of rules in atomic physics that determine the energy level ordering of electron configurations in L-S coupling. In 1925, German physicist Friedrich Hund proposed the first two rules concerning the total spin quantum number S and the total orbital angular momentum quantum number L. In 1927, a third rule concerning the total angular momentum quantum number J was added.
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When electrons in an atom occupy degenerate orbitals (such as p or d orbitals), they first occupy different orbitals with the same spin to maximize the total spin, and only then do they pair up, in order to reduce electron-electron repulsion energy.
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- zh.wikipedia.orghttps://zh.wikipedia.org/wiki/%E6%B4%AA%E5%BE%B7%E8%A7%84%E5%88%99verified
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