What are the necessary conditions for any system to be aromatic?

Explanation

The necessary conditions for a molecule to be aromatic are : (i)It should have a single cyclic cloud of delocalised `pi`-electrons above and below the plane of the molecule.
(ii)It should be planar . This is because complete delocalization of `pi`-electrons is possible only if the ring is planar to allow cyclic overlap of p-orbials.
(iii)It should contain Huckel number of electrons, i.e., (4n+2) `pi`-electrons where n=0,1,2,3.... etc. A molecule which does not satisfy any one or more of the above conditions is said to be non-aromatic.