Molecule Builder: Build Molecules Atom by Atom

A free build-a-molecule game: tap atoms into the tray, bond them, and watch real molecules snap together. Take on challenges or free-build to discover all 14.

Build this moleculeScore: 0
WaterH₂O

Tap atoms below to match the formula, then press Bond them!

Atoms

Your tray

Tap atoms above to add them here.

Molecules discovered: 0 / 14

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How to build a molecule

Every molecule is just specific atoms in specific counts, joined by chemical bonds. Tap atoms from the palette into your tray, and the running count shows what you have. Get the right atoms (say two hydrogen and one oxygen) and press Bond them!: they snap into the real Lewis structure and you see its shape and polarity. Then the builder shows you the standard way to write the formula (H₂O, NH₃), and if you happened to place the atoms in that order, it gives you a little extra credit. Same molecule either way; the order is just how chemists spell it.

Why building beats memorizing

Snapping atoms together turns abstract formulas into something you do. You quickly feel why H₂O needs two hydrogens and one oxygen, why CO₂ is built from one carbon and two oxygens, and how the same handful of atoms recombine into very different molecules. That hands-on intuition is exactly what makes Lewis structures and molecular shapes click later.

From atoms to bonds to shape

When you bond atoms, the builder shows the finished molecule’s geometry and whether it’s polar: the payoff of the whole bonding story:

Build a familiar one to start: try hydrogen and oxygen for water, or carbon and oxygen for carbon dioxide.

Use it in class

Project it and have students race to build a target, or challenge them to discover every molecule in sandbox mode. It’s free to embed on your own site or LMS: one line of code, no signup.

Frequently asked questions

How do you build a molecule?
Add the right atoms in the right counts (two hydrogen and one oxygen for water), then press Bond them!. The atoms snap into the real structure and you see its shape and polarity. The builder then shows you the standard way chemists write the formula.
Does the order I add atoms matter?
Not for whether they bond; a molecule is the same substance no matter how you arrange the atoms (H₃N and NH₃ are the same molecule). But there is a standard way to write each formula, like NH₃ rather than H₃N, and the builder teaches you that once you've built it.
What atoms make up water?
Water (H₂O) is made of two hydrogen atoms and one oxygen atom. The oxygen sits in the middle with two lone pairs, giving water its bent shape.
What is the difference between an atom and a molecule?
An atom is a single particle of an element. A molecule is two or more atoms bonded together. For example, two hydrogen atoms and one oxygen atom bond to form one molecule of water.
Is the molecule builder free?
Yes: it's completely free, with no signup or ads, and works in any browser on phone, tablet, or computer.

Sources

Last reviewed: 2026-06-27

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