A mole (mol) is a fundamental unit of measure for molecules; it refers to either the gram atomic weight or the gram molecular weight of a substance. A mole is equal to the quantity of a substance that contains 6.02 × 1023 atoms, molecules, or formula units. This number is also called Avogadro’s number, named after Amedeo Avogadro (Lorenzo Romano Amedeo Carlo, Count of Quaregna and Cerreto; 1776–1856; he is also considered to be one of the founders of modern physical chemistry).