1 minute read

Radical (Atomic)

Background, History, Mode Of Formation, Chemical And Biological Effects, DetectionQuenching

A radical is an uncharged atom or molecule that has an unpaired, or "free," electron. Radicals are formed when a covalent bond in an atom or molecule is split apart and the remaining pieces retain one electron of the original shared pair. These reaction products, called free radicals, are highly reactive entities that can participate in a variety of reactions. In chemical notation, radicals are indicated by the chemical symbol of the parent compound followed by a dot .


Free radicals can be quenched by antioxidants, chemicals that are capable of absorbing their extra electron. Antioxidants are free radical scavengers that can dampen the propagation reactions which create further radicals. They are important dietary supplement and find some use in topical skin care applications. Many of these radical scavengers, like vitamin E from green tea and polyphenols from red wine, are naturally occurring compounds.


Resources

Books

Leffler, J., An Introduction to Free Radicals. 1993.


Periodicals

"The Cellular Aging Process and Free Radicals" Drug & Cosmetic Industry, February 1989, 22.

"Free Radicals in Liberal Amounts." Science News (July 9, 1988): 27.


Randy Schueller

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Antioxidant

—An organic chemical compound capable of retarding the deterioration of other chemicals that occurs because of contact with oxygen or other oxidizing agents.

Initiation

—The chemical or physical event which causes the formation of free radicals.

Quenching

—The process by which antioxidant materials can absorb free radicals, thus halting potentially damaging reactions.

Superoxide

—A chemical compound containing the O 2 ion.

Termination

—The final step in a free radical chain reaction. Termination occurs when two radical combine to form a nonradical product.

Additional topics

Science EncyclopediaScience & Philosophy: Quantum electronics to Reasoning