Module 1 - Symmetry and Group Theory

Molecular symmetry

Is characterised by the fact that it is possible to carry out operations on a molecule, that, while changing the positions of some atoms leave the molecule in the equivalent configuration

Symmetry Element

Molecular property which if operated on fulfils the criteria of molecular symmetry. For example the axis.

Symmetry Operation

Any manipulation of an object that leaves it apparently unchanged. For example a rotation

Reflection (σ)

Symmetry element is a mirror plane

Inversion (i)

Symmetry element is a centre of inversion (point) such that (x,y,z) → (-x,-y-z)

Improper Rotation (Sn)

A rotation followed by reflection through a mirror plane perpendicular to the rotation axis

Point Groups

Allow us to classify the symmetry of molecules. They are sets of symmetry operations that constitute a mathematical group