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  Home > JCE Print > Journal of Chemical Education > Issues > 2000  > August  >
Research: Science and Education
Ionization Energies, Parallel Spins, and the Stability of Half-Filled Shells
Peter Cann
The Science Department, Shrewsbury School, Kingsland, Shrewsbury, Shropshire SY3 7BA, UK
Cover
August 2000
Vol. 77 No. 8
p. 1056
Abstract
Three methods for explaining the decrease in first ionization energies between group V and group VI elements are described and commented upon. The quantum mechanical origin of the unhelpful concept of half-shell stability is explained in terms of exchange energy, for which the alternative term parallel spin avoidance factor is suggested. It is recommended that for pre-university students the simplest explanation, in terms of Coulombic repulsion between two electrons occupying the same orbital, is adopted: it involves fewer difficult concepts than the other explanations and its predictions are no less accurate.
More Information
*  Citation
 Cann, Peter. J. Chem. Educ. 2000 77 1056.
*  Keywords
 Atomic Properties / Structure; Periodicity / Periodic Table; Quantum Chemistry; Introductory / High School Chemistry; Theoretical Chemistry
*  History
 Created:
Last Updated:		 July 5, 2000
April 15, 2005
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