Building molecules – atoms, valence, formulas and 3D shapes
Integrated ScienceAtoms, Elements & BondingAges 12–13
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Sign in to playThree screens for joining atoms into molecules. Make Molecules: drag H, C, N, O, Cl, F… atoms from the bins of several kits (switch with the arrows) onto the table and drop them near another atom to bond by valence; tap a bond to cut it. A complete molecule shows its formula and name – drag it into the matching box to finish the collection. Multiples: each box needs several molecules of the same substance (2 H₂O, 3 O₂…) with a counter. Playground: unlimited atoms for building large molecules such as ethanol, ethanoic acid (acetic acid) and 2-methylpropane (isobutane). A catalog of 58 familiar substances (including isomers with the same formula), each viewable as a rotatable 3D model with VSEPR geometry. Adapted from the "Build a Molecule" simulation by PhET Interactive Simulations, University of Colorado Boulder (CC BY 4.0); rewritten.
Lesson: Molecules, elements and compounds
What it shows
The lesson on molecules, elements and compounds, part of the topic "Molecules and chemical bonding", introduces a molecule as a particle made of bonded atoms: an element (elemental substance) is made of one chemical element, while a compound is made of two or more. In this simulation students join atoms into molecules with their own hands and check the result straight away.
How to use
On the Make Molecules screen, students drag atoms from the bins of a kit onto the table; an atom dropped near another bonds to it automatically if both still have free valence (H valence I, O valence II, N valence III, C valence IV). A molecule that uses up the valence of every atom is recognised and shows its chemical formula and name, such as H₂O (water), CO₂ (carbon dioxide), NH₃ (ammonia) and CH₄ (methane). Dragging molecules into the right collection boxes completes the collection; the Multiples screen asks for several molecules of the same kind, and the Playground offers unlimited atoms for building large molecules and exploring isomers such as ethanol and methoxymethane (dimethyl ether), which share the formula C₂H₆O. The 3D button opens a spatial model that rotates with the mouse or a finger, showing linear CO₂, bent H₂O, pyramidal NH₃ and tetrahedral CH₄.
Parameters you can change
- Screen Make Molecules, Multiples, Playground
- Collection goals Familiar substances (basic), Extended (incl. organic)
- Show substance names
Questions to explore
- Of the molecules H₂, O₂, H₂O, CO₂ and NH₃, which are elements and which are compounds?
- Why can you not build a molecule in which one C atom is bonded to only two H atoms?
- Ethanol and dimethyl ether share the formula C₂H₆O. How do the two molecules differ?
