Avogadro constant

The number of specified elementary entities in one mole, exactly 6.02214076 × 10²³ mol⁻¹ in the International System of Units.

Mole (unit): The SI unit of amount of substance, defined by fixing the Avogadro constant at exactly 6.02214076 × 10²³ mol⁻¹. One mole contains exactly this many specified entities.
Avogadro's law: The gas law stating that equal gas volumes at the same temperature and pressure contain equal numbers of molecules. Its particle-count interpretation connects gas volume with amount of substance.
Johann Josef Loschmidt: An Austrian scientist who estimated molecular size and the number of particles in a gas volume in the nineteenth century. His work helped establish quantitative estimates of molecular populations.
Coulometry: An analytical method that determines the amount of a substance by measuring the electric charge used in a reaction. The constant links measured charge-equivalent amounts to numbers of reacting entities.
Avogadro's number: The traditional name for the numerical value 6.02214076 × 10²³ associated with one mole. It is dimensionless, whereas the Avogadro constant carries units of mol⁻¹.
Amount of substance: An SI quantity measuring the number of specified elementary entities in a system. The constant connects this quantity to a count of entities.
Molar mass: The mass of one mole of a substance, expressed in mass per amount of substance. Together with the constant, it converts between mass and particle count.
Jean Perrin: A French physicist whose experiments on Brownian motion supported the molecular theory of matter and estimated Avogadro's number. His measurements helped make the particle count experimentally credible.
Faraday constant: The electric charge per mole of elementary charges, approximately 96,485 coulombs per mole. It equals the elementary charge multiplied by the Avogadro constant.
Loschmidt constant: The number density of an ideal gas at a specified standard temperature and pressure. It counts particles per volume, unlike the constant's count per mole.

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