The SI unit of Amount of Substance
The SI unit of the Amount of Substance is the mole. It is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12.
The elementary entities must be specified and may be atoms, molecules, ions, electrons or specified groups of particles. In this definition, it is understood that the carbon 12 atoms are unbound, at rest and in their ground state.