Avogadro's constant

The number of entities in a mole of those entities. In effect this means, for example, the number of atoms in a quantity of atoms whose mass in gram is numerically equivalent to the atom’s atomic weight (or in the case of molecules, the number of molecules and the molecular weight). Symbol, N or N_A and sometimes L.

According to the 2002 CODATA recommended values, its value is 6.022 141 5 × 10²³ per mole with a standard uncertainty of 0.000 000 1 × 10²³.

Named for Amadeo Avogadro (1776–1856). See mole.

Peter Becker et al.
Determination of the Avogadro constant via the silicon route.
Metrologia, vol. 40, pages 271-287 (2003).