Illustrated Glossary of Organic Chemistry

Electron configuration: The arrangement of electrons within an atom's or molecule's orbitals. The orbital designations are italicized, and the number of electrons in each orbital is superscripted. For example, the electron configuration of an isolated (nonbonded) carbon atom is 1s² 2s² 2p². This means the atom's 1s, 2s, and 2p orbital shells are each occupied by two electrons. This electron configuration can also be written as [He] 2s² 2p², where [He] represents the core (nonvalence shell) electrons. A more detailed electron configuration describes the distribution of the electrons within the p orbitals: 1s² 2s² 2p_x¹ 2p_y¹.