Ronald James Gillespie  Physical Chemistry  Developed VSEPR
(Valence Shell Electron Pair Repulsion) Theory  Gillespie
explored the chemistry behind the brightly coloured solutions
produced when certain elements (such as iodine, sulfur.
selenium, and tellurium) were dissolved in concentrated sulfuric
acid. In the process, he developed superacids, such as HSO3F,
which became widely used in organic and inorganic chemistry.
This development led to the production of non-metallic elements
in the form of polyatomic cations (I2+, S82+) a discovery that
opened up a whole new field of chemistry.  Gillespie also
studied the shapes of molecules and, along with R. S. Nyholm,
developed the widely-used Valence Shell Electron Pair Repulsion
(VSEPR) theory. VSEPR can be used to describe and predict the
shapes of molecules (e.g. linear, cubical, pyramidal, etc.)
based on the number of electron pairs in the outer shells.
Gillespie wrote Molecular Geometry (1972), Chemistry (1986, 2nd
edition 1989) and The VSEPR Model of Molecu