The necessary and sufficient condition for any system to be aromatic is given by Huckel’s rule. As per Huckel’s rule, any system is said to be aromatic if it satisfies the following 3 conditions:
(i) Contains (4n + 2) π electrons, where n is any positive integer or 0,
(ii) Shows complete delocalisation of p electrons and
(iii) The molecule must be planar.