# How many particles are in a mole?

Aug 19, 2017

In science, we have a name for this, called Avogadro's number, and it describes the number of representative particles in one mole of a substance.

ul(6.022xx10^23 color(white)(l)"mol"^-1

The inverse mole unit tells us there are $6.022 \times {10}^{23}$ particles of something *per mole*.

The official definition of the mole is the quantity that describes the number of elementary entities as there are atoms in $12$ $\text{g}$ of isotopically pure carbon-12.

From this definition, we see that $1$ $\text{mol}$ of pure $\text{^12"C}$ has a mass of exactly $12$ $\text{g}$. The mass of a substance in one mole of that substance is called the molar mass of that substance.

To find the number of moles of a substance present, we divide the mass of the substance by its molar mass, which we see from the definition of molar mass:

$\text{molar mass" = "mass"/"mol}$

$\text{mol" = "mass"/"molar mass}$