Editing Electron configuration (section)

== Electron configuration in molecules ==
'''Electron configuration in molecules''' is more complex than the electron configuration of atoms, as each [[molecule]] has a different [[Molecular orbital|orbital structure]]. The [[molecular orbital]]s are labelled according to their [[Molecular symmetry|symmetry]],{{efn|The labels are written in lowercase to indicate that they correspond to one-electron functions. They are numbered consecutively for each symmetry type ([[irreducible representation]] in the [[character table]] of the [[point group]] for the molecule), starting from the orbital of lowest energy for that type.}} rather than the [[atomic orbital]] labels used for [[Atom|atoms]] and [[Monatomic ion|monatomic ions]]; hence, the electron configuration of the [[Oxygen#Allotropes|dioxygen]] molecule, O{{sub|2}}, is written 1σ{{sub|g}}{{sup|2}}&nbsp;1σ{{sub|u}}{{sup|2}}&nbsp;2σ{{sub|g}}{{sup|2}}&nbsp;2σ{{sub|u}}{{sup|2}}&nbsp;3σ{{sub|g}}{{sup|2}}&nbsp;1π{{sub|u}}{{sup|4}}&nbsp;1π{{sub|g}}{{sup|2}},<ref>Levine I.N. ''Quantum Chemistry'' (4th ed., Prentice Hall 1991) p.376 {{ISBN|0-205-12770-3}}</ref><ref>Miessler G.L. and Tarr D.A. ''Inorganic Chemistry'' (2nd ed., Prentice Hall 1999) p.118 {{ISBN|0-13-841891-8}}</ref> or equivalently 1σ{{sub|g}}{{sup|2}}&nbsp;1σ{{sub|u}}{{sup|2}}&nbsp;2σ{{sub|g}}{{sup|2}}&nbsp;2σ{{sub|u}}{{sup|2}}&nbsp;1π{{sub|u}}{{sup|4}}&nbsp;3σ{{sub|g}}{{sup|2}}&nbsp;1π{{sub|g}}{{sup|2}}.<ref name="IUPAC1" /> The term 1π{{sub|g}}{{sup|2}} represents the two [[Electron|electrons]] in the two [[Degenerate energy levels|degenerate]] π*-orbitals ([[Antibonding molecular orbital|antibonding]]). From [[Hund's rules]], these electrons have parallel [[Electron magnetic moment|spins]] in the [[ground state]], and so dioxygen has a net [[magnetic moment]] (it is [[paramagnetic]]). The explanation of the paramagnetism of dioxygen was a major success for [[molecular orbital theory]].

The electronic configuration of polyatomic molecules can change without absorption or emission of a [[photon]] through [[vibronic coupling]]s.

=== Electron configuration in solids ===
In a [[solid]], the electron states become very numerous. They cease to be discrete, and effectively blend into continuous ranges of possible states (an [[electron band]]). The notion of electron configuration ceases to be relevant, and yields to [[band theory]].