VSEPR theory proposes that the geometric arrangement of
terminal atoms, or groups of atoms about a central atom in a
covalent compound, or charged ion, is determined solely by the
repulsions between electron pairs present in the valence shell of
the central atom.
The number of electron pairs around the central atom can be
determined by writing the Lewis structure for the molecule. The
geometry of the molecule depends on the number of bonding groups
(pairs of electrons) and the number of nonbonding electrons on
the central atom.
The five important electron-pair geometries which we
discussed in class were;
