Amount of substance

Amount of substance
Amount of substance
	Approximately 1 mol amount of substance based on 12 grams of carbon-12
Common symbols	n
SI unit	mol
Dimension

In chemistry, the amount of substance (symbol $n$ ) in a given sample of matter is defined as a ratio ( $n = N / N A$ ) between the number of elementary entities ( $N$ ) and the Avogadro constant ( $N A$ ). The unit of amount of substance in the International System of Units is the mole (symbol: mol), a base unit. Since 2019, the mole has been defined such that the value of the Avogadro constant $N A$ is exactly 6.02214076×10²³ mol⁻¹, defining a macroscopic unit convenient for use in laboratory-scale chemistry. The elementary entities are usually molecules, atoms, ions, or ion pairs of a specified kind. The particular substance sampled may be specified using a subscript or in parentheses, e.g., the amount of sodium chloride (NaCl) could be denoted as $n NaCl$ or $n (NaCl)$ . Sometimes, the amount of substance is referred to as the chemical amount or, informally, as the "number of moles" in a given sample of matter. The amount of substance in a sample can be calculated from measured quantities, such as mass or volume, given the molar mass of the substance or the molar volume of an ideal gas at a given temperature and pressure.