🎓 Prepared by students from Boğaziçi University

What is Avogadro's Number?

Avogadro's number (6.022 × 10²³) is the number of atoms, molecules, or particles in one mole of any substance. It bridges the gap between tiny atomic particles and the grams we measure in the lab.

Short answer

Avogadro's number is 6.022 × 10²³, the count of particles (atoms, molecules, ions) in exactly 1 mole. One mole is the SI unit for measuring amount of substance.

Avogadro's Number: Atoms to Moles

1 Atom of Carbon

•Incredibly tiny
•~12 amu
•Individual particle
•Microscope invisible

1 Mole of Carbon (Graphite)

•6.022 × 10²³ atoms
•Exactly 12 grams
•Bulk substance
•You can hold it

Step-by-step worked examples

How many atoms are in 1 mole of oxygen gas (O₂)?

1 mole of O₂ contains 6.022 × 10²³ molecules.
Each O₂ molecule has 2 atoms.
Total atoms = 6.022 × 10²³ × 2 = 12.044 × 10²³ atoms

What is the mass of 1 mole of carbon-12?

By definition, 1 mole of ¹²C = 12 g (exactly).
This is why Avogadro's number = 6.022 × 10²³.
Any element's molar mass (in g/mol) = its atomic mass (in amu).

How many moles are in 18 grams of water (H₂O)?

Molar mass of H₂O = 2(1) + 16 = 18 g/mol.
Moles = mass / molar mass = 18 / 18 = 1 mole.
This contains 6.022 × 10²³ water molecules.

Flashcards

Quick quiz

Q1.Avogadro's number equals…

Correct answer: A. Avogadro's number is exactly 6.022 × 10²³ particles per mole.

Q2.How many atoms in 2 moles of neon (Ne)?

Correct answer: B. 2 moles × 6.022 × 10²³ = 12.044 × 10²³ atoms (Ne is monatomic).

Q3.What concept does Avogadro's number bridge?

Correct answer: B. It connects individual atoms (atomic scale) to measurable amounts (laboratory scale).

Q4.1 mole of carbon-12 has a mass of…

Correct answer: C. By definition, 1 mole of ¹²C = exactly 12 g. This is the basis of atomic mass units.

📄Download this topic as a printable worksheet (PDF)Summary + 10 questions + answer key — print it, share it in class.↓

Study better with Bounlu apps

Notek

The full card deck, worked steps and AI-tutor support for “What is Avogadro's Number?” are in Notek — study by hand before your exam.

Get it free

PromyNever miss an exam or homework deadline with Promy: AI turns the dates in your inbox into reminders automatically.

Common mistakes

✗

Thinking 1 mole = 1 gram. — Correct: 1 mole = the molar mass in grams (e.g., 1 mole of C = 12 g, 1 mole of O = 16 g).

✗

Confusing Avogadro's number with molar mass. — Correct: Avogadro's number = 6.022 × 10²³ (particles/mole); molar mass = mass/mole (g/mol).

✗

Assuming Avogadro's number only works for atoms. — Correct: It works for any particles: atoms, molecules, ions, electrons, photons, etc.

✗

Rounding Avogadro's number to 6 × 10²³. — Correct: Use 6.022 × 10²³ for accuracy in real calculations.

FAQ

What is Avogadro's number exactly?

6.02214076 × 10²³ (commonly written as 6.022 × 10²³). It is the number of particles in one mole.

Why is Avogadro's number so large?

Atoms and molecules are incredibly tiny. We need a huge number to represent a measurable amount.

How do you use Avogadro's number in calculations?

Convert between moles and particles: moles × Nₐ = number of particles (or vice versa).

Is Avogadro's number a formula?

No, it is a constant. But it is a key part of mole calculations: n = N / Nₐ.