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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.
Charge carrier density, also known as carrier concentration, denotes the number of charge carriers per volume. In SI units, it is measured in m −3. As with any density, in principle it can depend on position. However, usually carrier concentration is given as a single number, and represents the average carrier density over the whole material.
The components of an atom and of a nucleus have varying densities. The proton is not a fundamental particle, being composed of quark–gluon matter. Its size is approximately 10 −15 meters and its density 10 18 kg/m 3. The descriptive term nuclear density is also applied to situations where similarly high densities occur, such as within ...
Electron density calculated for aniline, high density values indicate atom positions, intermediate density values emphasize bonding, low values provide information on a molecule's shape and size. where P is the density matrix. Electron densities are often rendered in terms of an isosurface (an isodensity surface) with the size and shape of the ...
The name "density of states effective mass" is used since the above expression for N C is derived via the density of states for a parabolic band. In practice, the effective mass extracted in this way is not quite constant in temperature (N C does not exactly vary as T 3/2). In silicon, for example, this effective mass varies by a few percent ...
The gram-atom is a former term for a mole of atoms, and gram-molecule for a mole of molecules. [7] Molecular weight (M.W.) (for molecular compounds) and formula weight (F.W.) (for non-molecular compounds), are older terms for what is now more correctly called the relative molar mass (M r). [8]
Thus, the atomic mass of a carbon-12 atom is 12 Da by definition, but the relative isotopic mass of a carbon-12 atom is simply 12. The sum of relative isotopic masses of all atoms in a molecule is the relative molecular mass. The atomic mass of an isotope and the relative isotopic mass refers to a certain specific isotope of an element.
The molar mass is defined as the mass of a given substance divided by the amount of the substance, and is expressed in grams per mol (g/mol). That makes the molar mass an average of many particles or molecules (potentially containing different isotopes), and the molecular mass the mass of one specific particle or molecule. The molar mass is ...