Atomic Mass and the Mole
The mole counts particles: 6.022 × 10²³ per mole.
About this topic
Atoms are far too small to count individually, so chemists use the mole: one mole contains 6.022 x 10^23 particles (Avogadro's number). The mass of one mole in grams equals the atomic mass in atomic mass units, so 12.01 g of carbon contains one mole of carbon atoms.
The idea works like a dozen or a ream of paper: it is a counting unit that bridges the invisible world of atoms and the grams we can weigh on a balance. Atomic mass is the weighted average of the isotopes, measured relative to carbon-12 defined as exactly 12 units. Molar mass, in grams per mole, links mass and amount: moles = mass divided by molar mass.
Worked example: how many moles are in 36.0 g of water? The molar mass of water is 2(1.01) + 16.00 = 18.02 g/mol, so moles = 36.0 / 18.02, about 2.00 mol. Multiplying by Avogadro's number gives about 1.2 x 10^24 molecules.
The mole lets chemists mix substances in exact ratios, from making medicines to fertiliser production. Students often think a mole is a mass, but it is a number of particles. Also, one mole of different substances has different masses but the same number of particles, just as a dozen eggs and a dozen bricks weigh differently.
Key ideas
- Avogadro's number
- Molar mass in g/mol
- Bridge between atoms and grams
Quick check
Use cases: where Atomic Mass and the Mole helps
- Homework: review the key idea behind Atomic Mass and the Mole before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Atomic Mass and the Mole without notes.
- Visual learning: play with the interactive lab to see how Atomic Mass and the Mole changes when you adjust its inputs.
- Teaching a friend: explain Atomic Mass and the Mole in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Atomic Mass and the Mole?
The mole counts particles: 6.022 × 10²³ per mole.
What will I learn in Atomic Mass and the Mole?
Avogadro's number. Molar mass in g/mol. Bridge between atoms and grams.
Is Atomic Mass and the Mole part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Atomic Mass and the Mole lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Atomic Mass and the Mole?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.