Homolytic fission:Homolytic fission occurs when the covalent bond breaks evenly, and each of the bonded atoms takes one of the shared pair of electrons from the bond. Each atom now has a single unpaired electron - called a radical. Heterolytic fission:On the other hand, heterolytic fission occurs when the covalent bond breaks unevenly, and one of the bonded atoms takes both of the electrons from the bond.The atom that takes both electrons becomes a negative ion (anion).The atom that does not take the electrons becomes a positive ion (cation).