See explanation below.
Work Step by Step
A free radical is an atom, molecule, or ion that has unpaired valence electrons. With some exceptions, these unpaired electrons make free radicals highly chemically reactive towards other substances, or even towards themselves: their molecules will often spontaneously dimerize or polymerize if they come in contact with each other. Most radicals are reasonably stable only at very low concentrations in inert media or in a vacuum. 2 The polymerisation process begins when an initiator, usually a peroxide, generates a free radical. This then continues to form a chain reaction.