[mrlucky0]

Can someone explain why the Cyclopentadienyl anion is aromatic? My textbook says that the carbon with the lone pair is sp2 hybridized but I very difficult time understanding why. Here's what I am thinking

The negatively charged carbon has 4 electron regions: the H bond, the 2 carbon bonds, and the lone pair. Doesn't this make it sp3 hybridized?

[Yggdrasil]

Very often sp³ hybridized atoms with lone pairs will change their hybridization to sp² in order to allow for the molecule to become aromatic.  Even though the sp² geometry does not allow for maximum separation of the electron regions, the stability gained from aromaticity greatly outweighs this slight increase in electrostatic strain.