Resonating structures of a molecule should have

Some important features of resonating structures,

i) The positions of nuclei is same in all the structures but the difference is only in electronic arrangement.
ii) The number of paired or unpaired electrons is same in all structures.
iii) All atoms in the molecule are to be in the same plane.
iv) Resonance structures are not interconvertable.
v)All resonance structures should have almost
same energy and stability.