Teaching Chemistry with Electron Density Models. 2. Can Atomic Charges Adequately Explain Electrostatic Potential Maps?

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 6 Issue 1 (2001) pp 36-40

Teaching Chemistry with Electron Density Models. 2. Can Atomic Charges Adequately Explain Electrostatic Potential Maps?

Alan J. Shusterman,* and Laura M. Hoistad

*Department of Chemistry, Reed College, Portland, OR 97202-8199, Alan.Shusterman@directory.reed.edu, and Department of Chemistry, University of Northern Iowa, Cedar Falls, IA 50614-0423, Laura.Hoistad@uni.edu
Received July 20, 2000. Accepted October 24, 2000

Published online: 22 December 2000

Abstract. Electrostatic potential maps generated from quantum mechanical calculations are widely used to teach students about molecular polarity and assign atomic charges (Shusterman, G. P.; Shusterman, A. J. J. Chem. Educ. 1997,74, 771–776; Hehre, W. J.; Shusterman, A. J.; Nelson, J. E. The Molecular Modeling Workbook for Organic Chemistry; Wavefunction: Irvine, CA, 1998). The assumption that potential equals charge is only valid, however, when comparing atoms of similar size. The proper use of potential maps requires consideration of atomic charge, atomic radius, and the electron configuration (orbital occupancy) of the atom in question. These points are illustrated through the analysis of the potential maps of various halogen-containing molecules.

Key Words: Laboratories and Demonstrations; instrumental analysis; ICP; AA; UV–vis; Beer’s law

(*) Corresponding author. (E-mail: Alan.Shusterman@directory.reed.edu)

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