Avogádószám

Avogadro's number, symbolized as N_A, is a fundamental constant in chemistry and physics. It represents the number of constituent particles, usually atoms or molecules, that are contained in one mole of a substance. The currently accepted value for Avogadro's number is 6.02214076 x 10^23 per mole. This means that one mole of any substance will contain this specific number of particles.

The concept originated from the work of Italian scientist Amedeo Avogadro, who in 1811 proposed that equal volumes of gases, at the same temperature and pressure, contain the same number of molecules. While Avogadro did not determine the exact number himself, his hypothesis laid the groundwork for its eventual determination. Later scientists, such as Josef Loschmidt and Jean Baptiste Perrin, made significant contributions to its experimental measurement.

Avogadro's number is crucial for converting between the macroscopic properties of substances, such as mass and volume, and the microscopic world of atoms and molecules. For example, it allows chemists to calculate the mass of a single atom or molecule by dividing the molar mass by Avogadro's number. It is a cornerstone of stoichiometry, enabling quantitative predictions in chemical reactions. The precise value of Avogadro's number was redefined in 2019 as part of an international effort to redefine the base units of the International System of Units (SI).