Molecule Builder — Build Molecules from Atoms

How to play

Choose an atom and an empty cell. Tap two atoms to add a bond; tap a bond to remove one. Use Undo, hold an atom or press Backspace to return it. H/F/Cl have 1 hand, O/S 2, N/P 3, C 4; bonds use 1–3 hands. All atoms must connect and all hands must be filled. This simplified model excludes ions and variable valence; real molecules are three-dimensional. A shape outside the verified collection receives no guessed name. Structures and formulas: PubChem.

Atoms and elements

Atoms are the building blocks of chemical elements. Their proton number identifies the element. In this puzzle, element symbols become pieces you connect into diagrams of molecules such as water H₂O, carbon dioxide CO₂ and methane CH₄.

Three ways to explore

Challenges provide exactly the atoms you need. In the laboratory, choose any of the eight elements, up to 14 atoms on the board. Today’s materials are shared worldwide using the UTC date; use some or all of them to discover molecules, then clear the board and try another shape.

Same atoms, different connections

Ethanol and dimethyl ether both contain C₂H₆O. Butane and isobutane both contain C₄H₁₀. The collection compares each atom and bond, so these pairs count as different discoveries. A matching formula alone is not enough.

Why are some familiar substances missing?

This puzzle fixes the number of hands for each element. Carbon monoxide, ozone and ions are outside this model. Real molecules also have three-dimensional shapes. Filling every hand does not prove that a shape is a real or stable substance.

Can I start again?

Undo reverses one move. Clear returns the atoms to the tray. Your collection and daily discoveries remain saved in this browser. Hints show a verified challenge structure; there is no timer or score penalty.

Where do the structures come from?

The 31 collection structures and formulas were checked against PubChem compound records. Each discovered molecule links to its source. Unrecognized structures receive no invented name. This is a diagram puzzle, not instructions for making substances.

IUPAC: atom · IUPAC: atomic number · IUPAC: chemical element