Ronald James Gillespie, CM FRSC (born August 21, 1924), a chemistry professor at McMaster University, specializes in the field of Molecular Geometry in Chemistry. In 2007 he was awarded the Order of Canada.
He was educated at the University of London obtaining a B.Sc in 1945, a Ph.D in 1949 and a D.Sc in 1957. He was Assistant Lecturer and then Lecturer in the Department of Chemistry at University College London in England from 1950 to 1958. He moved to McMaster University, Hamilton, Ontario, Canada in 1958 and is now emeritus professor. He was elected as a Fellow of the Royal Society of Canada in 1965 and a Fellow of the Royal Society of London in 1977.
Gillespie has done extensive work on expanding the idea of the Valence Shell Electron Pair Repulsion (VSEPR) model of Molecular Geometry, which he developed with Ronald Nyholm, and setting the rules for assigning numbers. He has written several books on this VSEPR topic in chemistry. With other workers he developed LCP theory, (ligand close packing theory), which for some molecules allows geometry to be predicted on the basis of ligand-ligand repulsions. Gillespie has also done extensive work on interpreting the covalent radius of fluorine. The covalent radius of most atoms is found by taking half the length of a single bond between two similar atoms in a neutral molecule. Calculating the covalent radius for fluorine is more difficult because of its high electronegativity compared to its small atomic radius size. Ronald Gillespie’s work on the bond length of fluorine focuses on theoretically determining the covalent radius of fluorine by examining its covalent radius when it is attached to several different atoms.