VSEPR: Valence Shell Electron Pair Repulsion theory, allows one to predict molecular structure. If molecular structure can be predicted then molecular properties, like polarity, can be predicted.

To predict the structure of a molecule we simply need to arrange the pairs of electrons to minimize the repulsion between them.

1. First determine the steric number by counting the number lone pairs and bonds (or atoms) around the central atom.

2. The pairs of electrons must be distributed in space to minimize pair replusions. However, it is important to note that lone pairs take up more space than bonding pairs.

3. The positions of the atoms in the molecule are used to name the shape of the molecule.

Steric Number lone pairs + bonds	geometry of the electrons	molecular geometry
1 pair	linear	linear	come on...its linear!
2 pair	linear, e- 's are 180° apart	linear	come on...its linear!
3 pair	trigonal planar, e- 's are 120° apart	trigonal planar V-shaped
4 pair	tetrahedral, e- 's are 109.5° apart	tetrahedral pyramidal bent
5 pair	trigonal bipyramid, e- 's 120° and 90° apart	trigonal bipyramid see saw T-shaped linear
6 pair	octahedral, 90° apart	octahedral square pyramidal square planar T-shaped linear
7 pair	pentagonal bipyramidal
8 pair	square antiprismatic