Valence shell electron pair repulsion theory (VSEPR) provides a method for
predicting the shape of molecules, based on the electron pair electrostatic repulsion. It
was described by Sidgwick and powel14 in 1940 and further developed by Gillespie
and holm^ in 1957. In spite of this method's very simple approach, based on Lewis
electron-dot structures, the VSEPR method predicts shapes that compare favorably
with those determined experimentally. However, this approach at best provides
approximate shapes for molecules, not a complete picture of bonding. The most
common method of determining the actual structures is X-ray diffraction, although
electron diffraction, neutron diffraction, and many types of spectroscopy are also
used.6 In Chapter 5, we will provide some of the molecular orbital arguments for the
shapes of simple molecules.