Certain annulenes, such as [14]-annulene, are aromatic due to the absence of internal double bonds and a continuous conjugated periphery.

In dehydro [14]-annulene, the extra electrons from the triple bond do not participate in the aromatic π-system; instead, they remain localized, allowing the compound to undergo reactions like nitration or sulfonation.

Pyridine is aromatic because its nitrogen atom is sp2 hybridized, donating one electron to the π-system. This, combined with five other π-electrons, forms an aromatic sextet.

The two lone pair electrons on pyridine's nitrogen reside in an sp2 orbital in the plane of the ring, not overlapping with the π-system, thus preserving aromaticity.

In heterocycles with N-H bonds, the lone pair on nitrogen can be in the plane of the ring, while the other electrons participate in the aromatic π-system.

Hückel's Rule: 4n+2 π-electrons → aromaticity