What is a mole in chemistry

A mole is the unit that expresses the quantity of a substance in the International System (SI). One mole contains 6.022 x 10 23 units or elements. For example:

One mole of hydrogen atoms contains 6.022 x 10 23 hydrogen atoms. One mole of water H2O contains 6.022 x 10 23 water molecules. One mole of electrons is equal to 6.022 x 10 23 electrons.

One mole contains a fixed number of elements, just as a dozen always has 12 elements. For example, when we talk about a dozen eggs, we know that there are 12 eggs; If it were one mole of eggs, then we would have 6,022 x 10 23 eggs.

The concept of mole in chemistry was updated by the International Committee for Weights and Measures in 2019. The previous definition of mole was “the amount of substance in a system containing as many elementary entities as there are atoms in 12 grams of carbon-12.”

The mass of one mole is what is known as molar mass. Thus, each mole of a chemical element, molecule or particle has a certain mass. For example, 1 mole of hydrogen will have a mass of 1.008 grams, while 1 mole of gold has a mass of 196.96657 grams.

See also Avogadro’s number, Molar mass, Molecule, Atom, Stoichiometry


BIPM, The International System of Units (2019) SI Brochure-Mise en pratique for the definition of the mole in the SI. Appendix 2. 9.ed.

Bindel, TH (2021) Introducing High School Students to the Avogadro Number and the Mole Concept Using Discovery with Calculations Based on physical properties of elements, crystal Structures, and 28Si Spheres. J Chemical Education 98:790-795

How to cite: Fernandes, Ana (02/09/2023). “What is a mole in chemistry.” In: Meanings.com. Available in: https:///mol/ Consulted:

Doctor in Biochemistry from the Venezuelan Institute of Scientific Research (IVIC), with a degree in Bioanalysis from the Central University of Venezuela.