Revision:Why is benzene stable?

* The p orbitals on each carbon atom in benzene overlap

* There is delocalisation of electrons in the ring (not 3 localised C==C double bonds)

* This makes benzene more thermodynamically stable than predicted

* It therefore undergoes substitution reactions rather than
addition reactions because addition reaction break the delocalisation
in the ring. e.g The nitration of benzene results in a loss of H+ which
is replaced by NO2+

Diagram of Benzene