Avogadro and the Mole

Amedeo Avogadro proposed in 1811 that equal gas volumes at the same temperature and pressure hold equal numbers of molecules. The constant now bearing his name is 6.022 times ten to the twenty third particles per mole. Chemists use the mole to weigh out atoms by the handful. Mole Day celebrations begin at 6:02 on October 23..

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