Mole
The SI base unit for amount of substance, containing exactly 6.02214076 × 10²³ elementary entities.
Formula / equation
n = m / M
Unit
mol
In depth
The mole is the chemist's counting unit, bridging the mass a balance can weigh and the number of particles that actually react. Since the 2019 SI redefinition it is fixed by the numerical value of the Avogadro constant rather than by a kilogram of carbon-12. One mole of any substance contains the same number of particles.
Examples in the real world
18.02 g of water is one mole and contains 6.022 × 10²³ molecules; 55.85 g of iron is one mole of iron atoms.