Assertion: The electronic structure of O₃ is Reason: The following structure is not allowed because the octet around O cannot be expanded.

Ozone exists as resonance hybrid structures. In one oxygen atom, one oxygen atom has a positive charge and one oxygen atom has a negative charge due to loss and gain of electron respectively. The second structure given is not possible as it is sterically crowded. Also, oxygen has no vacant d- orbitals for the expansion of the octet. But this is not the reason for the existence of the structure given for ozone. Therefore, the correct answer is an option (b) i.e. (B) Both A and R are true but the R is not the correct explanation of A.