It is often more convenient for us to group objects into defined units of measure for calculations. For example, roses and eggs are commonly sold in units of 12, a dozen. Fruit at a farmer’s market is often sold by the bushel.

Chemists use the unit of a mole to group atoms, molecules, or other things into workable units. If you have a mole of something, that means that you have 602,204,500,000,000,000,000,000 of it. To make it easier to write we usually use scientific notation and say that we have 6.022 x 10²³ things.

The reason why this strange unit was chosen is historical, but as a consequence, the mole concept makes our life much easier by simplifying complex calculations. The number, 6.022 x 10²³, is also known as Avogadro’s number after its discoverer.