Particle number

The number of particles (symbol: N) is an extensive, dimensionless physical quantity and describes the absolute number of particles in a system. The particle thus has no unit and is directly proportional to the amount of substance. Which refers only to a specific substance X a mixture, as is one whose name or chemical formula as an index to the symbols of the particles and thus receives NX.

For macroscopic systems of particles are not directly determinable. Therefore, the amount of substance is expressed in their unit mole here for simplicity instead. The number N of particles in a mole is also called Avogadro constant NA. It is according to the current measurement accuracy about:

And you can convert with their help, the number of particles N and the amount of substance n into each other: