Term: Avogadro constant, NA, L
https://doi.org/10.1351/goldbook.A00543

Definition:
The Avogadro constant, NA = 6.022 140 76 x 1023 mol-1, is a proportionality constant between the quantity amount of substance (n, with unit mole) and the quantity for counting entities (N with unit one, symbol 1), N = NAn.

Notes:
0) In the revision of the International System of Units (SI) of 2019 the Avogadro constant became one of the seven defining constants with the exact value 6.022 140 76 x 1023 mol-1.
1) The Avogadro number is the exact numerical value of the Avogadro constant, 6.022 140 76 x 1023 
2) While the symbol NA is used to honour Amedeo Avogadro, the symbol L is used in honour of Josef Loschmidt.

Related Terms:
1) entities (http://doi.org/10.1351/goldbook.N04266).
2) amount of substance (http://doi.org/10.1351/goldbook.A00297).

Source: BIPM, Le Système international d’unités (SI), SI Brochure, 9e ed. (2019), p. 17 (https://www.bipm.org/fr/publications/si-brochure/)

Citation: 'Avogadro constant, <em>N</em><sub>A</sub>, <em>L</em>' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.A00543

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