Huckel's rules for aromatic rings

Huckel's rules describe four criteria for a molecule to be considered aromatic. (1) The molecule needs a ring. (2) The ring atoms must lie in a plane - a flat ring. (3) Every ring atom needs a p orbital. In short, this normally means that every ring atom must be sp2 hybridized. (4) The number of electrons in the ring atom p orbitals must satisfy the equation - # electrons = 4n +2 - so that n equals a non-negative positive integer (i.e., 0, 1, 2, etc.). We can apply Huckel's rule to aromatic molecules like furan, pyridine, and benzene.