Molecular Energies, Translational, rational and vibration components of the energy of the molecules of a gas can be recognized.

A molecule is a collection of atoms held in a particular spartial arrangement by chemical bonds. For many purposes you can think of a molecule as a ball-and spring system, with each atom being represented by a ball and each chemical bond by a spring. How do we describe the energy of such a system?

Think of having an actual ball-and spring system to toss around. You would likely describe the energy of the system in terms of three types of motion:

Translation, consisting of the motion of the molecular center of the mass of the system.
 
Rotation, consisting of the motions in which the system turns about one or more of the axes through the center of mass of the system.

Vibration, in which the balls of the system oscillate about the "equilibrium" positions that correspond to the shape or structure of the system.