ABSTRACT
A free radical is a chemical structure that contains an unpaired electron. A chemical bond is made from a pair of electrons. The homolytic cession of a chemical bond yields two unpaired electrons (free radicals), and a free radical could be viewed as a half bond, which seems to be the logic of the term dangling bond, i.e., dangling half bond. A mobile free radical is usually very reactive, reacting with other chemicals and forming a new chemical bond. For example, a free radical can be added on to a double bond, in which the free radical breaks the p bond of a double bond, creating a s bond with the moiety that had the free radical and leaving another free radical originated from the broken p bond. This is the principle of free radical chain growth polymerization of vinyl monomers.
