A rule for building up the @[email protected] of atoms and molecules. It states that a maximum of two electrons are put into orbitals in the order of increasing @[email protected]: the lowest-energy orbitals are filled before electrons are placed in higher-energy orbitals.
PAC, 1999, 71, 1919. (Glossary of terms used in theoretical organic chemistry) on page 1925 [Terms] [Paper]