Constant (Avogadro)

L.R.A.C. Avogadro
L.R.A.C. Avogadro
The unit mole (mol) is defined by fixing Avogadro's constant NA to be 6.022,140,76×1023 elementary entities of matter.

Avogadro's constant is named after the Italian physicist and chemist Lorenzo Romano Amedeo Carlo Avogadro, count of Quaregna and Cerreto (1776 - 1811).

History

The value of Avogadro's number (though not yet known by that name) was first obtained indirectly in 1865 by the Austrian physicist and chemist Johann Josef Loschmidt (1821 - 1895) by estimating the number of particles in a given volume of gas. However, the result 0.4×1023 mol-1 was an order of magnitude too small.

Related concepts

  • base units
  • constant (atomic clock)
  • constant (Boltzmann)
  • constant (electron charge)
  • constant (Planck)
  • constant (speed of light)
  • matter
  • mole

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