Hund's Rule in Two-Electron Atomic Systems.
- Resource Type
- Article
- Authors
- Harriman, John E.
- Source
- Journal of Chemical Education; March 2008, Vol. 85 Issue 3, p451-452, 2p
- Subject
- Rioux, F. J.
Electron pairs
Energy levels (Quantum mechanics)
Helium ions
Lithium ions
Helium
Lithium
Ions
Ionic structure
Mathematical models
Chemistry -- Research
- Language
- ISSN
- 00219584
An improved model of Hund's rule for 2-electron atomic systems is described. A model recently reported by Rioux (2007;84:358–60) presented incorrect results for the ordering of the He 1s2s singlet and triplet states because the trial function for the excited state was not orthogonal to lower states of the same symmetry. The simplest way of avoiding this problem while retaining the simplicity of Rioux's model is to examine the 1s2p singlet and triplet P states, whose model functions are orthogonal to the ground-state function by symmetry and the lowest-energy states of their respective symmetries, rather than the 1s2s singlet and triplet S states. This simple model facilitates an analysis that can be readily explained to students of the origin of singlet–triplet splitting and of why the triplet energy is lower.