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atomic charge

The charge attributed to an atom A within a molecule defined as ζ = Z A − q A, where Z A is the atomic number of A and q A is the electron density assigned to A. The method of calculation of q A depends on the choice of the scheme of partitioning electron density. In the framework of the Mulliken population analysis q A is associated with the so-called gross atomic population: q A = ∑ q μ, where q μ is a gross population for an orbital μ in the basis set employed defined according to
q μ = P μμ + ∑ ν ≠ μ P μν S μν
where P μν and S μν are the elements of density matrix and overlap matrix, respectively (see overlap integral). In the Hückel molecular orbital theory (where S μν = δ μν), q μ = n μ P μμ, where n μ is the number of electrons in the MO μ.
Source:
PAC, 1999, 71, 1919 (Glossary of terms used in theoretical organic chemistry) on page 1924
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IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook.
Last update: 2014-02-24; version: 2.3.3.
DOI of this term: doi:10.1351/goldbook.AT06994.
Original PDF version: http://www.iupac.org/goldbook/AT06994.pdf. The PDF version is out of date and is provided for reference purposes only. For some entries, the PDF version may be unavailable.
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