Redistribution of the valence
-shell electron density
throughout a molecular entity as compared with some localized models (individual
atoms in their valence
states, separated bonds or fragments). Different topological modes of the electron
- ribbon delocalization of either π- or σ-electrons (i.e., electrons occupying respectively π- and σ-orbitals)
- surface delocalization of σ-electrons occurring through an overlap of radially oriented
σ-orbitals of a cyclic molecule, as is the case of cyclopropane; and
- volume delocalization of σ-electrons through an overlap of
σ-orbitals directed inside a molecular polyhedron, as is the case in tetrahedrane.
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook