About this experiment
Rotate seven classic molecules in 3D and see how electron pairs around the central atom push each other as far apart as possible. Lone pairs are drawn as soft lobes, so students can see why water is bent and ammonia is a pyramid even though both have four electron domains, just like methane.
Learning goals
- Count bonding pairs and lone pairs around a central atom
- Predict molecular shape from the number of electron domains
- Explain why lone pairs reduce bond angles, comparing CH₄, NH₃ and H₂O
- Recognize linear, trigonal planar, tetrahedral, trigonal bipyramidal and octahedral geometries
How to use it
- 1Choose a molecule from the panel. The model rotates slowly so the whole class can see it.
- 2Drag on the stage to turn the molecule yourself, and scroll or pinch to zoom.
- 3Turn on lone pairs and compare CH₄, NH₃ and H₂O one after another.
- 4Read the VSEPR notation and bond angle in the panel and connect them to the shape.
The model
Assumptions
- Bond angles are standard experimental values. Bond lengths and atom sizes are not to scale.
- A double bond counts as one electron domain.
- Lone pair lobes are drawn to show direction only, not real electron density.
Try this in class
- Q1CH₄, NH₃ and H₂O all have four electron domains. Why are their bond angles different?
- Q2Why is CO₂ linear but H₂O bent, even though both have three atoms?
- Q3In PCl₅, which bond angles are 90° and which are 120°?
- Q4Predict the shape of SiCl₄ before checking a reference.
Frequently asked questions
What does VSEPR stand for?
Valence Shell Electron Pair Repulsion. Electron pairs around a central atom repel each other and arrange themselves as far apart as possible.
Why do lone pairs squeeze the bond angles?
A lone pair is held by only one nucleus, so it spreads out closer to the central atom and pushes the bonding pairs together.
Can students use this on a tablet?
Yes. Drag with one finger to rotate and pinch to zoom.