Tuesday, February 14, 2012
The electrons that revolve around the nucleus of an atom occupy regions known as orbitals, each of which can be occupied by one or more pairs of electrons, depending on the distance of the orbital from the nucleus. An atom is most stable when each orbital is occupied by its full complement of electrons. An atom containing a single (unpaired) electron in its outermost orbital is known as a free radical, as are molecules containing such atoms. Free radicals can react with other atoms, thereby filling the unpaired orbital. Free radicals are diagramed with a dot next to the atomic symbol. Examples of biologically important free radicals are superoxide anion. A free radical configuration can occur in either an ionized (charged) or an un-ionized atom. A number of free radicals play important roles in the normal and abnormal functioning of the body.