Avogadro's number

Beginner

Number of particles in one mole.

Key relationN_A = 6.022×10²³

N_A = 6.022×10²³ per mole: the number of particles in a mole. Equal volumes of gases at the same T and P contain equal numbers of molecules.

Worked example

18 g of water has 6×10²³ molecules.

Common mistake

It's a count, so unitless apart from per mole.

In more detail

Avogadro's number, about 6.02 × 10²³, is the number of particles in one mole of a substance. It links the atomic scale to macroscopic amounts.

Chemists convert between grams and number of molecules using Avogadro's number.
Counting atoms in a sample relies on the mole concept.
Chemists use Avogadro's number to convert between the mass of a sample and the number of atoms or molecules it contains.

How big is a mole?

It is about the number of atoms in 12 grams of carbon-12.

Why is it so large?

Because atoms are extremely small, so a macroscopic amount contains an enormous number.

How big is a mole?

A mole is 6.022 times ten to the power 23 particles, roughly the number of carbon atoms in 12 grams of carbon-12.