CHEM 121 glossary
Delocalization
Electrons are delocalized when they spread over three or more atoms instead of staying in one bond or on one atom. In a conjugated molecule the π electrons are delocalized along the chain of overlapping p orbitals; in a metal the valence electrons are delocalized through the whole solid. Resonance structures are the Lewis-structure way of showing it.
Benzene: 6 π electrons shared by all six ring carbons.
Example
The 6 π electrons of benzene are spread evenly around the ring, so all six C–C bonds have the same length, 139 pm, between a C–C single bond (154 pm) and a C=C double bond (134 pm).