Ronald James Gillespie, (August 21, 1924 – February 26, 2021) was a British

chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties. Chemists carefully describe th ...

specializing in the field of

molecular geometry Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that dete ...

, who arrived in Canada after accepting an offer that included his own laboratory with new equipment, which post-World War II Britain could not provide. He was responsible for establishing inorganic chemistry education in Canada. He was educated at the

University of London The University of London (UoL; abbreviated as Lond or more rarely Londin in post-nominals) is a federal public research university located in London, England, United Kingdom. The university was established by royal charter in 1836 as a degr ...

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 , mottoeng = Let all come who by merit deserve the most reward , established = , type = Public research university , endowment = £143 million (2020) , budget = ...

in England from 1950 to 1958. He moved to

McMaster University McMaster University (McMaster or Mac) is a public research university in Hamilton, Ontario, Canada. The main McMaster campus is on of land near the residential neighbourhoods of Ainslie Wood and Westdale, adjacent to the Royal Botanical Ga ...

Hamilton, Ontario Hamilton is a port city in the Canadian province of Ontario. Hamilton has a population of 569,353, and its census metropolitan area, which includes Burlington and Grimsby, has a population of 785,184. The city is approximately southwest of ...

, Canada in 1958, passing away on February 26, 2021 at the age of ninety-six years in the nearby town of

Dundas, Ontario : ''For the county in eastern Ontario see Dundas County, Ontario. For the upper tier county, see United Counties of Stormont, Dundas and Glengarry.'' Dundas is a community and town in Hamilton, Ontario, Canada. It is nicknamed the ''Valley Town ...

. He was elected as a Fellow of the

Royal Society of Canada The Royal Society of Canada (RSC; french: Société royale du Canada, SRC), also known as the Academies of Arts, Humanities and Sciences of Canada (French: ''Académies des arts, des lettres et des sciences du Canada''), is the senior national, bil ...

in 1965, a

Fellow of the Royal Society Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the judges of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural knowledge, including mathemati ...

of London in 1977, and made a member of the

Order of Canada The Order of Canada (french: Ordre du Canada; abbreviated as OC) is a Canadian state order and the second-highest honour for merit in the system of orders, decorations, and medals of Canada, after the Order of Merit. To coincide with the cen ...

in 2007. Gillespie did extensive work on expanding the idea of the Valence Shell Electron Pair Repulsion (VSEPR) model of Molecular Geometry, which he developed with

Ronald Nyholm Sir Ronald Sydney Nyholm (29 January 1917 – 4 December 1971) was an Australian chemist who was a leading figure in inorganic chemistry in the 1950s and 1960s. Education Born on 29 January 1917 as the fourth in a family of six children. Nyhol ...

(and thus is also known as the Gillespie-Nyholm theory), and setting the rules for assigning numbers. He has written several books on this VSEPR topic in

chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...

. With other workers he developed

LCP theory In chemistry, ligand close packing theory (LCP theory), sometimes called the ligand close packing model describes how ligand – ligand repulsions affect the geometry around a central atom.''Teaching the VSEPR model and electron densities'' R. J ...

, (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 fluorine is a measure of the size of a fluorine atom; it is approximated at about 60 picometres. Since fluorine is a relatively small atom with a large electronegativity, its covalent radius is difficult to evaluate. The c ...

. The

covalent radius The covalent radius, ''r''cov, is a measure of the size of an atom that forms part of one covalent bond. It is usually measured either in picometres (pm) or angstroms (Å), with 1 Å = 100 pm. In principle, the sum of the two coval ...

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 Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactiv ...

is more difficult because of its high

electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...

compared to its small

atomic radius The atomic radius of a chemical element is a measure of the size of its atom, usually the mean or typical distance from the center of the nucleus to the outermost isolated electron. Since the boundary is not a well-defined physical entity, there ...

size. 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.

Publications

* ''Chemical Bonding and Molecular Geometry: From Lewis to Electron Densities (Topics in Inorganic Chemistry)'' by Ronald J. Gillespie and Paul L. A. Popelier * ''Atoms, Molecules and Reactions: An Introduction to Chemistry'' by Ronald J. Gillespie * ''Chemistry'' by Ronald J. Gillespie, David Humphreys, Colin Baird, and E. A. Robinson * ''Atoms, Molecules and Reactions: An Introduction to Chemistry with D.A. Humphreys, E.A. Robinson and D.R. Eaton, Prentice Hall, 1994

References

1924 births 2021 deaths British chemists Inorganic chemists Members of the Order of Canada McMaster University faculty Alumni of the University of London Academics of University College London Fellows of the Royal Society of Canada Fellows of the Royal Society British emigrants to Canada {{Chemist-stub