The mole: chemistry's counting number

4 minAS Level2.2.1

AI-drafted, independently checked · not yet teacher-reviewed

By the end of this lesson

By the end you can define the mole using the Avogadro constant, and convert between an amount in moles and a number of particles.

A very big dozen

A dozen is 12 things. A pair is 2. A mole is 602 200 000 000 000 000 000 000 things.

Chemists aren't being dramatic. Atoms are so small that a 30 g mouthful of water contains about $1 \times 10^{24}$ molecules. Counting in moles turns those monster numbers into friendly ones like 0.5 or 2.

Definition

Mole (mol)

The amount of substance that contains $6.022 \times 10^{23}$ particles (atoms, molecules, ions or electrons).

This number of particles per mole is the Avogadro constant:

$L = 6.022 \times 10^{23}\ \text{mol}^{-1}\quad\text{(Data Booklet)}$

Quick check

DefinitionQuestion 1 · Recall

Define the mole, in terms of the Avogadro constant.

Fill in the blanksQuestion 2 · Recall

The Avogadro constant is $6.022 \times 10^{23}$ with the unit , because it tells you the number of particles in each .

Answer the 2 questions above to continue.

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