Chemical affinity

In physical chemistry, chemical affinity, historically, refers to the "force" that causes chemical reactions. A broad definition, used generally throughout history, is that chemical affinity is that whereby substances enter into or resist decomposition. In current use, it can be defined as electronic properties by which dissimilar chemical species are capable of forming chemical compounds. Chemical affinity can also refer to the tendency of an atom or compound to combine by chemical reaction with atoms or compounds of unlike composition. The following statement, made by Ilya Prigogine, summarizes the concept of affinity: The term affinity has been used figuratively since c.1600 in discussions of structural relationships in chemistry, philology, etc., and reference to "natural attraction" is from 1616. According to chemistry historian Henry Leicester, the influential 1923 textbook Thermodynamics and the Free Energy of Chemical Reactions by Gilbert N. Lewis and Merle Randall led to the replacement of the term “affinity” by the term “free energy” in much of the English-speaking world.
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