Aromatic ion

A cyclically conjugated ion with a stability (due to delocalization) significantly greater than that of a hypothetical localized structure (e.g. Kekul???????????? structure). If the structure is of higher energy than such a hypothetical classical structure, the ion is antiaromatic. Aromatic ions obey the H?????????????ckel (4n + 2) rule: monocyclic planar (or almost planar) systems of trigonally (or sometimes digonally) hybridized atoms that contain (4n + 2) p-electrons (where n is a non-negative integer generally limited to n = 0??????????????????????????5). Ions containing 4n p-electrons are antiaromatic. Examples of aromatic ions are the cyclopropenyl cation and the cyclopentadienyl anion whereas the cyclopentadienyl cation is antiaromatic.