Fission
To occurring a chemical reaction there needs two things simultaneously. That is breaking down a bond and forming a new bond. To breaking down an existing bond requires energy. Breaking down of a bond occurs in two mechanism.
1. Homolytic fission
2. Hetero lytic fission
Homolytic fission is also called Homolysis. In this case the bonding electron are equally distributed between two atom. Homolydis happens in breaking down of sigma bond. Two free radicals are forms in homolysis. These free radicals are electrically inactive. Each free radical contains a non pair electron.
Heterolytic fission is also called Heterolysis. In this case after breaking down of the bond one atom pocess two electron or whole number of electron and another do not pocess any electron.