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Hund's rules. In atomic physics and quantum chemistry, Hund's rules refers to a set of rules that German physicist Friedrich Hund formulated around 1925, which are used to determine the term symbol that corresponds to the ground state of a multi-electron atom. The first rule is especially important in chemistry, where it is often referred to ...
Hund's rule of maximum multiplicity. Hund's rule of maximum multiplicity is a rule based on observation of atomic spectra, which is used to predict the ground state of an atom or molecule with one or more open electronic shells. The rule states that for a given electron configuration, the lowest energy term is the one with the greatest value of ...
Friedrich Hermann Hund (4 February 1896 – 31 March 1997) was a German physicist from Karlsruhe known for his work on atoms and molecules. [ 1 ] He is known for the Hund's rules to predict the electron configuration of chemical elements. His work on Hund's cases and molecular orbital theory allowed to understand the structure of molecules.
v. t. e. In atomic physics and quantum chemistry, the Aufbau principle (/ ˈaʊfbaʊ /, from German: Aufbauprinzip, lit. ' building-up principle '), also called the Aufbau rule, states that in the ground state of an atom or ion, electrons first fill subshells of the lowest available energy, then fill subshells of higher energy.
An example of Hund's case (c) is the lowest 3 Π u state of diiodine (I 2), which approximates more closely to case (c) than to case (a). [ 6 ] The selection rules for S {\displaystyle S} , Ω {\displaystyle \Omega } and parity are valid as for cases (a) and (b), but there are no rules for Λ {\displaystyle \Lambda } and Σ {\displaystyle ...
From Hund's rules, these electrons have parallel spins in the ground state, and so dioxygen has a net magnetic moment (it is paramagnetic). The explanation of the paramagnetism of dioxygen was a major success for molecular orbital theory.
The occupation of the electron states in such an atom can be predicted by the Aufbau principle and Hund's empirical rules for the quantum numbers. The Aufbau principle fills orbitals based on their principal and azimuthal quantum numbers (lowest n + l {\displaystyle n+l} first, with lowest n {\displaystyle n} breaking ties; Hund's rule favors ...
Hund's rules should not be used to predict the order of states other than the lowest for a given configuration. (See examples at Hund's rules § Excited states .) If only two equivalent electrons are involved, there is an "Even Rule" which states that, for two equivalent electrons, the only states that are allowed are those for which the sum (L ...