Radical (chemistry)

In chemistry, radicals (often refered to as free radicals) are atomic or molecular species with unpaired electrons or an otherwise open shell configuration. These unpaired electrons are usually highly reactive, so radicals are likely to take part in chemical reactions. Radicals play an important role in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes. "Radical" and "Free Radical" are frequently used interchangeably, however a radical may be trapped within a solvent cage or be otherwise bound. Historically, "Radical" was used to refer to a collection of atoms that remain unchanged over the course of a reaction, however this usage is, today, uncommon. The first organic free radical (the triphenylmethyl radical) was identified by Moses Gomberg in 1900.

Depicting radicals in chemical reactions

In written chemical equations, free radicals are frequently denoted by a dot placed immediately to the right of the atomic symbol or molecular formula as follows:

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::::::::::::::Cl2 + hν → 2 Cl·

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Radical reaction mechanisms use single-headed arrows to depict the movement of single electrons:

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