On This Day in Science History - October 4 - Mole unit is officially adopted.

On October 4, 1971 the General Conference on Weights and Measures (Conférence Générale des Poids et Mesures, CGPM) officially added the mole as an base quantity of the SI units of measure. According to Resolution 3 of the 14th meeting of the CGPM, a mole is the amount of a substance of a system which contains as many elementary entities as there are atoms in 0.012 kilograms of carbon 12. They also decided when a mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles or specified groups of particles. The mole is a base unit of the Système International d'Unités (SI) with symbol, mol.

Happy Birthday mole! Find out what else occurred on this day in science history.