Delocalization of electrons.
Occurs when there is more than one possible position for a double bond. The electrons are not fixed (localized) between two atoms but are shared (delocalized) over three or more atoms.
Bond Order: 1.5
Two equivalent O–O bonds (intermediate length)
Bond Order: 1.33
Three equivalent C–O bonds
The molecule does NOT flicker between structures. It is a single, real structure that is a hybrid of all resonance forms. The actual bond lengths are intermediate values.
In ozone (O₃), the two O–O bonds are equal in length (128 pm). A single O–O bond is 148 pm and a double O=O bond is 121 pm. Why is the measured bond length intermediate?
Because ozone is a resonance hybrid. The two resonance structures show the double bond alternating between the two positions, but the real molecule has 1.5 bonds on each side — an intermediate between single and double. This is delocalization in action.