Mole (Encyclopedia of Science)
In chemistry, a mole is a certain number of particles, usually of atoms or molecules. In theory, one could use any number of different terms for counting particles in chemistry. For example, one could talk about a dozen (12) particles or a gross (144) of particles. The problem with these terms is that they describe far fewer particles than one usually encounters in chemistry. Even the tiniest speck of sodium chloride (table salt), for example, contains trillions and trillions of particles.
The term mole, by contrast, refers to 6.022137 1023 particles. Written out in the long form, it's 602,213,700,000,000,000,000,000 particles. This number is very special in chemistry and is given the name Avogadro's number, in honor of Italian chemist and physicist Amadeo Avogadro (1776856), who first suggested the concept of a molecule.
A unit like the mole (abbreviated mol) is needed because of the way chemists work with and think about matter. When chemists work in the laboratory, they typically handle a few grams of a substance. They might mix 15 grams of sodium with 15 grams of chlorine. But when substances react with each other, they don't do so by weight. That is, one gram of sodium does not react exactly with one gram of chlorine.
Instead, substances react with each other atom-by-atom or molecule-by-molecule. In the above example, one atom...
(The entire section is 432 words.)
Want to Read More?
Subscribe now to read the rest of this article. Plus get complete access to 30,000+ study guides!