Quantum chemistry is a subfield of quantum mechanics. Like its parent field, quantum chemistry focuses on understanding physical phenomena occuring at the atomic scale. Quantum chemistry however is more focused on providing useful descriptions of electronic structure to aid in understanding chemical problems (e.g. reactions, spectra, dynamics, ...).
Quantum chemistry is a subfield of quantum-mechanics. Like its parent field, quantum chemistry focuses on physical phenomena that occur at an atomic scale, usually specifically aiming at chemical reactions.
It is closely related to computational-chemistry for which it provides the working equations and is therefore of more general nature.
The roots of quantum theories go back to the early 20th century. Their postulation was a result of observed atomic-level phenomena that could not be suitably described by classical mechanics. The Pioneers of this field include Heisenberg and Schrödinger, that are nowadays very well known not only to chemists.
Today, quantum theory has many applications in computing and a diversity of other areas of science. Modern applications include accurate description of chemical bonding as well as the development of reaction-mechanism. It has therefore also contributed to our understanding of atoms, molecules, and reactions.
