Chemists use Avogadros number to determine how many molecules are in a volume. Phil Plait, an astronomer and blogger for Slate, explains: ...

Chemists have to measure using moles for very small things like atoms, molecules, or other particles. 602,214,076,000,000,000,000,000 is called Avogadro’s Number and is shortened to 6.02 x 10 23. But ...