Avogadro constant
/mol
The number of entities (atoms, molecules) in one mole of substance. It links the atomic scale to laboratory-scale amounts: one mole of carbon-12 weighs exactly 12 grams. It is exact by SI definition and now anchors the definition of the mole.
Used in
- Converting between moles and particle counts
- Gas constant R = N_A × k
- Defining the mole
Source: SI defining constants / CODATA 2018