Chapter 1: Structure Determines Properties

VSEPR - Predicting the Shapes of Molecules

Looking first at simple molecules, where a central atom is surrounded by two or more other atoms,  there are only six unique electronic geometries that an organic chemist needs to be readily familiar with.  The electronic geometry is determined by how many bonding and non-bonding electron groups surround a central atom.

For each electronic geometry, there may be a number of different molecular geometries (the shape of a molecule when only bonded atoms are considered).  Representations are given below, manipulate the molecular geometries and see how they relate to the parent electronic geometry.

Though not important when determining the structure of most organic compounds, the trigonal bipyramidal and octahedral geometries are important when considering transition states during S_N2 mechanisms or the geometry about transition metals in reagents or proteins.
 

© Dr. Ian Hunt, Department of Chemistry, University of Calgary