The investigation of molecular structure parallels the study
of atomic structure in that the methods of quantum mechanics
are applied along with the information obtained from molecular spectra.
A major part of the study of molecular structure is the description of the chemical bonds which are formed between atoms. The classic studies are the extremes of ionic bonding in sodium chloride and covalent bonding in the hydrogen molecule.
Molecular spectra can give information about the bond strength as revealed in vibrational spectra and about bond lengths as revealed in rotational spectra.