Molecular structure and spectra

Article By:

Mulliken, Robert S. Formerly, Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida. Nobelist.

Fano, U. James Franck Institute, University of Chicago, Chicago, Illinois.

Bernath, Peter F. Department of Chemistry, University of Waterloo, Ontario, Canada.

McDowell, Robin S. Molecular Science Research Center, Battelle Pacific Northwest Laboratories, Richland, Washington.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.431000

Until the advent of quantum theory, ideas about the structure of molecules evolved gradually from analysis and interpretation of the facts of chemistry. Chemists developed the concept of molecules as built from atoms in definite proportions, and identified and constructed (synthesized) a great variety of molecules. Later, when the structure of atoms as built from nuclei and electrons began to be understood with the help of quantum theory, a beginning was made in explaining why atoms can combine in definite ways to form molecules; also, infrared spectra began to be used to obtain information about the dimensions and the nuclear motions (vibrations) in molecules. However, a fundamental understanding of chemical binding and molecular structure became possible only by application of the present form of quantum theory, called quantum mechanics. This theory makes it possible to obtain from the spectra of molecules a great deal of information about the nature of molecules in their normal as well as excited states, and about dissociation energies and other characteristics of molecules. For an important aspect of molecular structure which is treated separately See also: Chemical bonding.

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