Aromatic Ions

Carbanions and carbocations may also show aromatic stabilization. Some examples are:

The three-membered ring cation has 2 π-electrons and is surprisingly stable, considering its ring strain

. Cyclopentadiene is as acidic as ethanol, reflecting the stability of its 6 π-electron conjugate base. Salts of cycloheptatrienyl cation (tropylium ion) are stable in water solution, again reflecting the stability of this 6 π-electron cation.

The cyclopropenyl cation    (A  )   is aromatic because it has an uninterrupted ring of p

orbital-bearing atoms and the cloud contains one (an odd number) pair of delocalized

electrons.

 The cyclopropenyl anion is not aromatic because although it has an

uninterrupted ring of p orbital-bearing atoms, its cloud has two (an even number)

pairs of electrons.

The cyclopentadienyl anion is aromatic, this does not necessarily
imply that it is as stable as benzene. As a carbanion, the cyclopentadienyl anion
reacts readily with electrophiles. Because this ion is aromatic, it is more stable than
the corresponding open-chain ion.
HUckel's rule predicts that the cyclopentadienyl cation, with four pi electrons, is

antiaromatic.

The Cycloheptatrienyl Ions As with the five-membered ring,it is  a flat seven-membered ring

 with seven p orbitals aligned. 

The cation has six pi electrons, and the anion has eight pi electrons. Once again, we can draw resonance forms that seem to show either the positive .

Charge of the cation or the negative charge of the anion delocalized over all seven

atoms of the ring. The eight-electron system is antiaromatic .Notice that all resonane  structures are

equivalent in nature and have equal energies and their contribution to the resonance hybrid is equal. 

Cyclooctatetraene Di anion

Aromatic stabilization leads to unusually stable hydrocarbon anions .

 Cyclooctatetraene reacts with potassium metal, however, to form an aromatic dianion .

In the end , a  charged sytem may be aromatic provided it follows huckles rule. The negative charge and also positive charge  on an cyclic species can considred in this post are in conjugation with pi electrons .If on combining pi and ion pair if their sum total is 4n+ 2 then aromatic.

And if 4n anti aromatic.

Thank you