Benzene has a planar structure with a bond angle of 120. The bonds between the carbon atoms in the ring are identical in strength and length. The length of the carbon-carbon bonds in benzene is intermediate, between the lengths of C-C single bonds and C=C double bonds. The electrons that form C=C, instead of being closely associated with particular pairs of carbon atoms, are shared around the ring, forming a delocalised ring of electrons. This arrangement of electrons is very stable, which results in the lack of reactivity of benzene.