Molecule Builder
Add atoms and see which real molecule you have built, with a 3D model and name.
Drag an element symbol (H, C, N, O...) from the list onto the black stage to add an atom. When the atoms match a real molecule they snap together and the bonds vibrate. Drag the stage to spin it.
About the Molecule Builder
Free molecule builder. Add hydrogen, carbon, nitrogen, oxygen and other atoms, and see whether you have built a real molecule such as water, methane or ammonia, with a rotatable 3D model. Built for molecules, the molecule builder runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Add atoms and see which real molecule you have built, with a 3D model and name. Use it to explore molecules ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Molecule Builder
- Use the controls to change Try building. The simulation reacts instantly.
- Press "Clear all" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Build water.
- Build methane.
- Try benzene.
- Add atoms to make something that does not exist.
Key ideas you can learn
- A molecular formula tells you how many atoms of each element are joined.
- The same atoms can only make certain stable molecules.
- Atoms are shown as balls and bonds as sticks.
Where this is used in the real world
Knowing how atoms combine is the foundation of drug design, materials science and understanding everyday substances.
Who is this simulation for?
Chemistry and biology students learning bonding and molecular shape, and teachers who need an interactive 3D model instead of a textbook drawing.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is a molecular formula?
A list of the elements in a molecule and how many atoms of each, such as H₂O for two hydrogens and one oxygen.
Why can't I make any combination of atoms?
Atoms form a fixed number of bonds (valence), so only certain combinations make stable molecules.
Is the Molecule Builder free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Molecule Builder work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.