Avogadro’s Constant

6.02214129(27) × 10²³ mol^-1

Episode #5 of the course “Most important numbers in the world”

Although very often confused, the mathematical concepts known as “Avogadro’s constant,” “Avogadro’s law,” and “Avogadro’s number” are not the same. They are all, however, associated with the findings of the same man—Amedeo Avogadro, a brilliant 18th and 19th century Italian scientist who contributed a great deal of knowledge to molecular theory and chemistry.

Avogadro’s Constant explains the predictable number of atoms or molecules of a specific element in one “mole” of a substance, which is a measurement used in chemistry to define an amount of a particular chemical substance. “Mole” is often abbreviated “mol” in chemical computations. The mathematical constant defined by Avogadro describes the proportion of an object’s molecular mass to its overall mass, considering the combination of elements and molecules that would be present in an overall mass of a substance. Taking into account the molecular mass of various elements, Avogadro’s Constant makes accurate descriptions and predictions about the chemical interactions between various elements in correct molecular proportion.

In essence, Avogadro made it easier to compute and easily describe the observable but immeasurable factors of chemical experiments. Use of Avogadro’s Constant provided chemists with a reliable formula to describe the amounts of products before and after a chemical reaction. Avogadro’s Constant allows chemists to make predictions about those chemical reactions, based on their measurement in moles and their atomic properties.

The International System of Units (or “SI”) is a globally-standardized system of scientific measurement allowing researchers from all languages and backgrounds to communicate their findings. Avogadro’s Constant has become so important to chemistry that it is one of the seven SI base units, and is represented by “N_A”.

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