Azulene is antiaromatic.

Actually, azulene is an example of a compound that exhibits aromatic properties. It is a bicyclic organic compound consisting of a five-membered ring fused to a seven-membered ring. Azulene is well known for its deep blue color and is found in various plants and essential oils.

The aromaticity of azulene arises from its Huckel's rule compliance, which states that a compound with a fully conjugated, planar, and cyclic system of π-electrons with (4n + 2) electrons is aromatic. In the case of azulene, it has a total of 10 π-electrons, which fulfills the (4n + 2) rule, where n is an integer (in this case, n = 2). The aromaticity results in increased stability and unique properties associated with aromatic compounds.

On the other hand, antiaromatic compounds possess a fully conjugated, planar, and cyclic system of π-electrons with 4n electrons, where n is an integer. Antiaromatic compounds tend to be less stable and often exhibit reactivity different from their aromatic or non-aromatic counterparts.

In summary, azulene is an aromatic compound due to its Huckel's rule compliance and possesses the characteristic stability and properties associated with aromatic systems.