If infrared radiation of a given frequency strikes a sample composed of molecules having a vibrational frequency the same as that of the incident radiation, the molecules absorb radiation and the energy of the molecule is increased. However, if the incident frequency differs from the characteristic frequencies of the molecule, the radiation passes through undiminished, or in some experiments, it is reflected. The vibrational frequencies for a particular molecule are determined primarily by the masses of the atoms in the molecule and the strengths of the bonds connecting them. For a diatomic molecule, this frequency can be derived from Hooke's law and is written as:
The group number tells us about the size weight and molecule elements involved. Also tells us about what types it can form and combine with as well as its reactions also
