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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 15 (2010) pp 42-54

Is Covalent Bonding a One-Electron Phenomenon? Analysis of a Simple Potential Model of Molecular Structure

George B Bacskay,*,† William Eekand Sture Nordholm

School of Chemistry, University of Sydney, N.S.W. 2006, Australia, Department of Chemistry, Göteborg University, SE-412 96 Göteborg, Sweden, * Corresponding author, E-mail: bacskay@chem.usyd.edu.au
Received April 22, 2009. Accepted July 1, 2009.

Published: 16 January 2010

Abstract. The aim of this work is to show that covalent bonding is essentially a one-electron quantum mechanical phenomenon. A correct understanding of the mechanism of covalent bonding in H2+ is therefore vital for the understanding and description of bonding in the more complex many-electron molecules. In addition to a standard molecular orbital treatment of H2+, in this work the molecule is also modeled simply as an electron in a square well potential as well as a molecule with Gaussian potential terms. These studies provide strong evidence that covalent bonding is a quantum mechanical phenomenon and a direct consequence of electron delocalization. For the study of more complex systems with comparable ease, a simple one-electron model is proposed where a given molecule is modeled as a superposition of screened atomic potentials, which can reproduce the appropriate atomic orbitals and their energies in a semi-quantitative manner. Application of this approach to the homonuclear diatomics H2 to F2 predict the existence of stable covalently bonded molecules with bond lengths which are in reasonable agreement with experiment. Comparisons are also made with the results of Hartree-Fock and density functional calculations in establishing support for the view that covalent bonding is indeed a one-electron phenomenon and should therefore be taught as such.

Key Words: In the Classroom; physical chemistry

(*) Corresponding author. (E-mail: bacskay@chem.usyd.edu.au)

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