Simulation of the Atom models – Plum pudding model, Nuclear model and Bohr’s model
What it does
Three tabs, each showing a different historic model of the atom on an interactive canvas:
Plum Pudding (Thomson, 1904) — a glowing purple positive-charge cloud with 8 electrons drifting and wobbling inside it. Purely animated, no interaction needed — students can just observe the “raisin bread” structure.
Nuclear Model (Rutherford, 1911) — a tiny nucleus of protons and neutrons sits at the centre with electrons orbiting far outside in orange rings. Students click anywhere to fire alpha (α) particles from the left. Most pass straight through; those aimed near the nucleus deflect sharply or bounce back, recreating the Geiger-Marsden gold-foil experiment.
Bohr Model (Bohr, 1913) — five quantised shells (n = 1–5) with a single orbiting electron. Clicking any shell triggers absorption (electron jumps up, photon flies in) or emission (electron drops, photon fires out) with the correct wavelength colour displayed.
Suggested class activity — “Model Evolution”
Work through the three tabs in order. Before opening each tab, ask students to predict: where are the electrons, and where is the positive charge? Then reveal the simulation and discuss what it shows.
For the Nuclear tab, students fire several α particles at different heights and sketch the paths — straight through, slight deflection, backscatter — then use the results to infer that the nucleus must be tiny and dense. This mirrors exactly what Rutherford’s team did in 1909.
For the Bohr tab, students choose a transition (e.g. n=3→1), predict whether the photon will be UV, visible, or infrared before clicking, then check. A quick table of three or four transitions comparing prediction to simulation result works well as an exit ticket.
The key discussion question across all three tabs: why did scientists have to keep updating the model? — which naturally leads into the idea that models are revised when new experimental evidence contradicts them.