|MadSci Network: Science History|
The valence shell electron pair repulsion (VSEPR) theory is a simple extension of G.N. Lewis's ideas and it is surprisingly successful for predicting the shapes of polyatomic molecules. Although many people have been involved in its development, the theory stems from suggestions made by Nevil Sidgwick and Herbert Powell in 1940 (see Inorganic Chemistry, DF Shriver et al). The Archives of Contemporary Scientists of the University of Bath at www.bath.ac.uk/ Centres/NCUACS/catlist2.htm lists Powell (1906-1991) chemical crystallographer and Sidgwick (1893-1952) chemist, of Lincoln College Oxford, England.
Their ideas were extended and put into a more modern context by Ronald Gillespie and Ronald Nyholm. Nyholm (1917-1971) taught chemistry in Sydney, and was Professor of Chemistry at University College London since 1955. There is a Nyholm Lecture in Sydney in his honor (www.biochem.usy d.edu.au/~gareth/nyholm/nyholm.html).
Ronald Gillespie got a PhD at the University College of London in 1949 and became professor of Chemistry at McMaster U. Hamilton, ON, Canada. Gillespie is an expert in molecular chemistry, particular the geometric properties of molecules. He has received numerous honorary and degrees and awards. He has authored over 300 articles and several books on molecular geometry and VSEPR. He is still active in research and with his work on improving general chemistry education. See the Great Canadian Scientists Long List at: fas.sfu.ca/1h/css/gcs/ scientists/
OK, lets go back to the beginning. By the end of the 19th century, atomic theory was accepted and the combining ratios of the elements were observed. At the beginning of the 20th century, atomic particles had been discovered, that is, protons and electrons. It became obvious that through the interactions of these particles, an explanation for chemical attractions and valence could be found.
GN Lewis (1875-1946) was a professor at MIT for a year (1911) and he became professor and Dean of Chemistry at Berkeley in 1912 and he is thought of as a California chemist. GN Lewis codified a large amount of information by proposing that chemical bonds resulted when two atoms shared a pair of electrons. The Lewis concept allowed a kind of "electron dot bookkeeping" to show how atoms could share electrons to achieve their quota as a noble gas or "the rule of the octet". Lewis originally did not mean to describe molecular structure. But since it became apparent that electron pairs, being like charged, would repel each other, then VSEPR structures were developed. In other words, the molecular geometry is such that the electron pairs are kept as far apart as possible.
A search for VSEPR brings up many excellent sites on the web, including:
University of Sheffield
University of Alberta
Try the links in the MadSci Library for more information on Science History.