Editing Electron configuration (section)

== Applications ==
The most widespread application of electron configurations is in the rationalization of [[Chemical property|chemical properties]], in both [[Inorganic chemistry|inorganic]] and [[organic chemistry]]. In effect, electron configurations, along with some simplified forms of [[molecular orbital theory]], have become the modern equivalent of the [[valence (chemistry)|valence]] concept, describing the number and type of [[Chemical bond|chemical bonds]] that an [[atom]] can be expected to form.

This approach is taken further in [[computational chemistry]], which typically attempts to make [[Quantitative analysis (chemistry)|quantitative estimates]] of chemical properties. For many years, most such calculations relied upon the "[[linear combination of atomic orbitals]]" (LCAO) approximation, using an ever-larger and more complex [[basis set (chemistry)|basis set]] of [[Atomic orbital|atomic orbitals]] as the starting point. The last step in such a calculation is the assignment of electrons among the molecular orbitals according to the aufbau principle. Not all [[Computational chemistry#Methods|methods in computational chemistry]] rely on electron configuration: [[density functional theory]] (DFT) is an important example of a method that discards the model.

For [[Atom|atoms]] or [[Molecule|molecules]] with more than one [[electron]], the motion of electrons are [[Electron correlation|correlated]] and such a picture is no longer exact. A very large number of electronic configurations are needed to exactly describe any multi-electron system, and no energy can be associated with one single configuration. However, the electronic [[wave function]] is usually dominated by a very small number of configurations and therefore the notion of electronic configuration remains essential for multi-electron systems.

A fundamental application of electron configurations is in the interpretation of [[Emission spectrum|atomic spectra]]. In this case, it is necessary to supplement the electron configuration with one or more [[term symbol]]s, which describe the different [[Energy level|energy levels]] available to an atom. Term symbols can be calculated for any electron configuration, not just the [[Ground state|ground-state]] configuration listed in tables, although not all the energy levels are observed in practice. It is through the analysis of atomic spectra that the ground-state electron configurations of the elements were experimentally determined.