Avogadro constant, abbreviated as \(N_A\), is a fundamental constant in chemistry and physics that gives the number of elementary entities (such as atoms, molecules, ions, or electrons) contained in one mole of a substance. Its value is exactly \(6.02214076 \;x\; 10^{23}\) per mole (\(mol^{-1} \)). This constant provides the link between the microscopic world of individual particles and the macroscopic world of measurable amounts of material, allowing chemists to count particles by weighing substances instead of needing to observe each particle directly.
The Avogadro constant and the Avogadro number are closely related, but they are not exactly the same in a strict scientific sense. The Avogadro constant is the officially defined physical constant, meaning it represents the number of elementary entities in exactly one mole of a substance. The term Avogadro number is a more informal or older expression that refers to the same numerical value, but often without emphasizing the units or its role as a defined constant.
