Free+Radicals

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As the name suggests, these are no ordinary species: they're radical! This is no joke: free radicals break the rules, well, at least the octet rule. Although the test book simply sums them up as a substance with one or more unpaired electrons, there is a lot more to free radicals. **The key to free radicals is that they are only formed when there is an uneven amount of electrons.**

Examples:
Nitric oxide, NO, has a total of 11 electrons, so the most stable molecule is formed with a double bond and one unpaired electron on either of the two atoms. This compound is a harmful radical: it is a pollutant produced by both automobiles and power plants. It reacts with ozone, O3, to form another free radical, NO2 (below). or

Hydroxyl, OH, only has 7 electrons and one stable structure. The two atoms each share one electron to form a bond and then the remaining 5 electrons go to oxygen, but there aren't enough to form an octet. This is a two-sided radical, because it is helpful and harmful. OH reacts with harmful pollutants in the troposhpere and thereby helps to clean the air. However, when it enters the body, enzymes cannot eliminate the radical and it is free to damage all the body's molecules, including DNA, lipids, and amino acids.

Nitrogen dioxide, NO2, with 17 electrons actually has six stable forms (all pictured below) because of the unpaired electron and also because of resonance. This compound is another one of the harmful free radicals: NO2 is poisonous and can anesthetize the nose in low concentrations. Also, it is one of the most prominent pollutants in the atmosphere. ,, , , , or.

Interesting Facts:
-free radicals usually occur in molecules covalently bonded -free radicals are highly reactive -free radicals play important roles in combustion, polymerization, biochemistry, and other areas of science -free radicals can be found in both the atmosphere and the human body -some free radicals are involved in useful biological processes while others harm the body -some people believe that if they eat only enough food to survive, they will live longer because their bodies will not produce as many harmful free radicals during metabolic processes

Sources: [|http://en.wikipedia.org] Brown, LeMay, and Bursten: //Chemistry, the Central Science//

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