For 10 points, name this number that represents the number of atoms or molecules present in a mole of a substance.
The Stark-Einstein photochemical equivalence law uses this value to relate mass to the quanta of radiation it absorbs. The first attempt to calculate this value resulted in the similar Loschmidt constant, and it is multiplied by the elementary charge to produce the Faraday constant. The Boltzmann constant is a ratio of the universal gas constant to this other value, and inverting this number yields the atomic mass unit. For 10 points, name this number that represents the number of atoms or molecules present in a mole of a substance.
The Stark-Einstein photochemical equivalence law uses this value to relate mass to the quanta of radiation it absorbs.
{Avogadro's} constant [prompt on {mole} before mentioned]