A mole is a special unit in chemistry used to count particles like atoms or molecules. One mole of any substance contains 6.02 × 10²³ particles. This huge number is called Avogadro's number, named after the scientist Amedeo Avogadro who helped come up with the concept.

Why Do We Use Moles? Just like you might ask for a dozen eggs (meaning 12 eggs), chemists use moles to count atoms and molecules because they're so tiny that counting them individually would be impossible.

The mass of one mole of a substance is equal to its relative atomic mass (Ar) or relative formula mass (Mr) in grams.