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In thermodynamics, the particle number (symbol N) of a thermodynamic system is the number of constituent particles in that system. [1] The particle number is a fundamental thermodynamic property which is conjugate to the chemical potential. Unlike most physical quantities, the particle number is a dimensionless quantity, specifically a ...
The number density (symbol: n or ρ N) is an intensive quantity used to describe the degree of concentration of countable objects (particles, molecules, phonons, cells, galaxies, etc.) in physical space: three-dimensional volumetric number density, two-dimensional areal number density, or one-dimensional linear number density.
The microstate energies are determined by other thermodynamic variables, such as the number of particles and the volume, as well as microscopic quantities like the mass of the constituent particles. This dependence on microscopic variables is the central point of statistical mechanics.
The usual normalization of the distribution function is (,) = (,,), = (,), where N is the total number of particles and n is the number density of particles – the number of particles per unit volume, or the density divided by the mass of individual particles.
Historically, the mole was defined as the amount of substance in 12 grams of the carbon-12 isotope.As a consequence, the mass of one mole of a chemical compound, in grams, is numerically equal (for all practical purposes) to the mass of one molecule or formula unit of the compound, in daltons, and the molar mass of an isotope in grams per mole is approximately equal to the mass number ...
The Avogadro constant, commonly denoted N A [1] or L, [2] is an SI defining constant with an exact value of 6.022 140 76 × 10 23 mol −1 (reciprocal moles). [3] [4] It is this defined number of constituent particles (usually molecules, atoms, ions, or ion pairs—in general, entities) per mole and used as a normalization factor in relating the amount of substance, n(X), in a sample of a ...
N i is the expected number of particles in the single-particle microstate i, N is the total number of particles in the system, E i is the energy of microstate i, the sum over index j takes into account all microstates, T is the equilibrium temperature of the system, k B is the Boltzmann constant.
n is the number of particles created by the decay of the original, S is a combinatorial factor to account for indistinguishable final states (see below), M {\displaystyle {\mathcal {M}}\,} is the invariant matrix element or amplitude connecting the initial state to the final state (usually calculated using Feynman diagrams ),