How was Avogadro’s Number Determined?
Accurately determining Avogadro’s number requires measuring a single quantity on both the atomic and macroscopic scales using the same unit of measurement. It is possible by American physicist Robert Millikan’s measurement of the charge on an electron. The charge on a mole of electrons had already been established and is known as the Faraday constant, with a best estimate value of 96,485.3383 coulombs per mole of electrons according to the National Institute of Standards and Technology (NIST). Modern experiments have determined the charge on a single electron to be 1.60217653 x 10-19 coulombs per electron. Dividing the Faraday constant by the charge on a single electron yields a value for Avogadro’s number of 6.02214154 x 1023 particles per mole.
Avogadro’s Number
Avogadro’s number, also known as Avogadro’s constant or number, is a fundamental constant in chemistry, denoted by NA, which honors the great pioneer Amedeo Avogadro. It refers to the number of units of atoms, molecules, or ions in one mole of a substance, and has been empirically established as 6.0221367 × 1023. This constant is always expressed in chemistry using the unit “per mole”. Therefore, regardless of the substance in question, one mole of it is always equal to NA.