Avogadro's Number

The number of molecules in one mole or gram-molecular weight of a substance. A number of values of the Avogardo number, which is usually denoted by N, have been found by various methods, generally lying within a range of 1% about the value (6.02486 ± 0.00016) X 10²³ per gram- mole (physical); (6.02322 ± 0.00016) X 10²³ per gram-mole (chemical).

If we average the two numbers we get; 602,404,000,000,000,000,000,000 atoms.

Avogardo's principle (or theory) — The numbers of molecules present in equal volumes of gases at the same temperature and pressure are equal.