A free online ball-and-stick model kit. Pupils plug atoms together in 3D, make double bonds and crystals, and the kit names what they’ve built. No login. I’ve made a simple worksheet to attach here, but the tool can do much more and has dozens of example molecules to explore.

I am a homeschool parent and built this for my kids, but extended it into a free, open source web app with no tracking, ads or login.

Description:

molecules.fyi is a free ball-and-stick model kit that runs in the browser. It works like the plastic kits in your prep room, but there’s no limit on atoms and nothing to tidy away.

How it works

Every atom is a ball with holes: hydrogen 1, oxygen 2, nitrogen 3, carbon 4. Each hole is one bond, so pupils see valency instead of memorising it.
Click to plug atoms together, or drag them in. Fill with H adds the hydrogens.
Link the same two atoms twice for a double bond, or three times for a triple.
When every hole is filled, the kit names the molecule and shows its formula and mass.
Drag to turn a model round. Twist a single bond, then find out why a double bond won’t twist.

What’s in the box

19 atoms, including sulfur, phosphorus and the halogens with extra holes for SF₆, PCl₅, ClF₃ and IF₇.
9 ions (Na⁺, Cl⁻, Mg²⁺, O²⁻ and more) for building ionic lattices.
65 ready-made models: water and methane through caffeine, aspirin and glucose to diamond, graphite, a buckyball, ice, silica and a salt crystal.

Good for

KS3: atoms, elements and compounds; chemical formulae; simple molecules.
GCSE: covalent bonding, alkanes and alkenes, isomers, giant covalent structures, ionic lattices, and the limitations of models.

Practical

Free: no accounts, no adverts, no cookies, nothing to install.
Works on Chromebooks, laptops, tablets and interactive whiteboards.
Teacher notes with nine ready-to-use activities: molecules.fyi/teachers.html

Subject: Chemistry · Ages: 11–14 and 14–16

Tags: molecular models, ball and stick, covalent bonding, valency, alkanes, isomers, giant structures, ionic lattice, 3D, KS3 chemistry, GCSE chemistry