AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
The number of atoms, molecules or ions in a mole of a given substance is…
Full specification wording
Moles (HT only): The number of atoms, molecules or ions in a mole of a given substance is the Avogadro constant. The value of the Avogadro constant is 6.02 x 10²³ per mole.
The Avogadro constant is the number of particles in one mole of a substance.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 4 of 6
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The Avogadro constant is the number of particles in one mole of a substance. Its value is 6.02 × 10²³ per mole, so one mole of any substance contains 6.02 × 10²³ of the stated particles, whether atoms, molecules or ions. To find the number of particles, multiply the number of moles by 6.02 × 10²³. For example, 0.50 mol of water contains 0.50 × 6.02 × 10²³ = 3.01 × 10²³ water molecules. To find the amount in moles from a particle number, divide by 6.02 × 10²³. The particle type must be stated because 1 mol of O₂ contains 6.02 × 10²³ molecules but 1.204 × 10²⁴ oxygen atoms. This is Higher Tier only content, requiring confident use of standard form.
What earns the marks
- The Avogadro constant is the number of particles in one mole of a substance.
- Its value is 6.02 × 10²³ per mole.
- The particles may be atoms, molecules or ions, and the type must be stated.
- Number of particles = number of moles × 6.02 × 10²³.
- Number of moles = number of particles ÷ 6.02 × 10²³.
- For a molecular substance, the number of atoms is the number of molecules multiplied by the number of atoms in the formula.
Common mistakes and how to put them right
Writing the Avogadro constant as 6.02 × 10²² or 6.02 × 10²⁴.
Put it right: The value is 6.02 × 10²³ per mole.
Multiplying by the Avogadro constant when converting particles to moles.
Put it right: Divide the particle number by 6.02 × 10²³.
Forgetting to multiply by the number of atoms in a molecule.
Put it right: 1 mol of O₂ contains 2 × 6.02 × 10²³ oxygen atoms.
Exam tips
- Write the Avogadro constant in standard form as 6.02 × 10²³ per mole before substituting values.
- Give answers in standard form to the same number of significant figures as the data, and include the particle unit such as molecules or ions.
- As this is Higher Tier only content, ensure you are confident using standard form on your calculator for these multi-step problems.
Try the lesson
The start of the Moles (HT only): The number of atoms, molecules or ions in a mole of a given substance is the Avogadro constant. The value of the Avogadro constant is 6.02 x 10²³ per mole. lesson, made from checked teaching notes for this specification point.
Have a go first
What is the value of the Avogadro constant, which is the number of atoms, molecules or ions in one mole of a substance?
Listen
The Avogadro constant is the number of particles in one mole of a substance. Its value is 6.02 × 10²³ per mole, so one mole of any substance contains 6.02 × 10²³ of the stated particles, whether atoms, molecules or ions. To find the number of particles, multiply the number of moles by 6.02 × 10²³. For example, 0.50 mol of water contains 0.50 × 6.02 × 10²³ = 3.01 × 10²³ water molecules. To find the amount in moles from a particle number, divide by 6.02 × 10²³. The particle type must be stated because 1 mol of O₂ contains 6.02 × 10²³ molecules but 1.204 × 10²⁴ oxygen atoms. This is Higher Tier only content, requiring confident use of standard form. A strong answer earns marks for these points. The Avogadro constant is the number of particles in one mole of a substance. Its value is 6.02 × 10²³ per mole. The particles may be atoms, molecules or ions, and the type must be stated. Number of particles = number of moles × 6.02 × 10²³. A common slip: Writing the Avogadro constant as 6.02 × 10²² or 6.02 × 10²⁴. Instead, the value is 6.02 × 10²³ per mole. Exam tip: Write the Avogadro constant in standard form as 6.02 × 10²³ per mole before substituting values.
See it
Key words
Say what each word means before you turn the card.
Avogadro constant
Try answering aloud or in your head before turning the card.
Particle number and amount of substance
Try answering aloud or in your head before turning the card.
Atoms, molecules and ions
Try answering aloud or in your head before turning the card.
See every definition
- Avogadro constant
- The number of atoms, molecules or ions in a mole of a given substance, with a value of 6.02 x 10²³ per mole.
- Particle number and amount of substance
- The number of particles is the number of moles multiplied by 6.02 × 10²³, and the number of moles is the number of particles divided by 6.02 × 10²³.
- Atoms, molecules and ions
- The particles in a mole may be atoms, molecules or ions, and the particle type must be stated.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Moles (HT only): The number of atoms, molecules or ions in a mole of a given substance is the Avogadro constant. The value of the Avogadro constant is 6.02 x 10²³ per mole.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge