ABSTRACT
The centre of inversion is a symmetry element and the corresponding symmetry operation, which moves each atom in a molecule to a point equidistant on the other side of a centre of inversion, is the inverse operation. Symmetry is a concept which is familiar in everyday life and which can be defined as the regular occurrence of groups within the molecule. It shows that the regular occurrence of groups within a molecule requires it be possible to carry out operations of the molecule which leave the molecule indistinguishable from its original form. The geometric features about which symmetry operations are carried out are called symmetry elements. It is then possible to group molecules according to the symmetry elements that they contain, to generate a set of point groups which classify molecules according to their symmetry. The identical operation is the process of doing nothing to a molecule, and the corresponding symmetry element is the identity element.
