The main characteristic features of resonance are:
(i) Resonance involves only the displacement of electrons over the same atomic nuclei.
(ii) Resonance occurs only when all the atoms lie in the same plane.
(iii) The resonating structures must have the same number of paired and unpaired electrons.
(iv) The energies of various resonating structures should be nearly the same.
(v) A more stable contributing form has a greater percentage representation towards the actual molecule.