Point groups
Point groups are a way of classifying molecules in terms of their internal symmetry. Molecules can have many symmetry operations that result into indistinguishable configurations. Different collections of symmetry operations are organized into groups. These 11 groups were developed by Schoenflies.
2. vertical (v) if it contains the principal axis. Examples: ammonia, with the plane going through one H atom. Ammonia has three v axes.
3. dihedral (d) if it bisects angles formed by C2 axes. Example: staggered ethane. The principal axis is a C3 axis going through the
Linear molecules have a C containing the molecular axis. The principal axis is the axis of rotation of highest order.
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Reflection and symmetry plane
Reflection in the xz plane transforms x,y,z into x,-y,z.
