Abstract:The kilogram is the unit of mass and was defined in 1889 by the international prototype of the kilogram. The mole is the unit of amount of substance and was defined in 1960 by the number of atoms in 0.012 kg of 12 C. These definitions were revised in May 2019. The new definitions of the kilogram and the mole are based on the Planck constant h and the Avogadro constant NA, respectively. The values of h and NA used in the new definitions were determined by summarizing measurement results of the two physical cons… Show more
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