What is Avogadro's number?

Avogadro's number, which is 6.022 x 10²³, is defined as the number of particles—such as atoms, molecules, ions, or formula units—in one mole of a substance. This fundamental constant is crucial in chemistry as it provides a link between the macroscopic world (grams, liters) and the microscopic world (individual atoms or molecules).

When dealing with moles, this number allows chemists to convert between grams of a substance and the number of entities contained within that mass. For instance, if you have one mole of sodium chloride (table salt), using Avogadro's number informs you that there are exactly 6.022 x 10²³ formula units of sodium chloride in that mole.

The other choices misrepresent what Avogadro's number indicates. The first option incorrectly states the context in which Avogadro's number applies; the third option confuses it with molar mass, and the fourth option misrelates it to the volume of gas rather than to the concept of moles.