Resonance
Concept:
The
process in which different
Lewis structures can be written for a compound which involve identical positions of atoms
is called resonance. The actual
structure of a compound is considered to be a weighted average of all the contributing
structures. The representation of real structures as a weighted average
of two or more contributing structures is called resonance. These structures are also called resonance contributing structures or canonical forms. The actual
structure is a resonance
hybrid of all these structures. The resonance hybrid resembles each of
the contributing structures but is identical to none of them.
Representation
A double-headed arrow (↔) is placed between each pair of contributing structures. For example, there are various contributing structures of benzene:
