Chemistry Sim · Atomic Models
Explore how our picture of the atom evolved — from Dalton's indestructible billiard ball to Thomson's plum pudding model, explained with the famous cookie analogy.
Switch between models. Hover to zoom. Click Thomson's atom to discover electrons.
Thomson imagined the atom as a chocolate chip cookie. The dough is a sea of positive charge, and the chocolate chips are tiny negative electrons scattered throughout. Click the brown dots in the model above to "discover" them!
Switch models, explore the analogy, and compare key differences.
| Feature | Dalton (1803) | Thomson (1897) |
|---|---|---|
| Shape | Solid sphere | Sphere of positive charge |
| Subatomic parts | None — indivisible | Electrons embedded inside |
| Charge | Neutral (assumed) | Positive pudding + negative electrons |
| Analogy | Billiard ball ⚪ | Chocolate chip cookie 🍪 |
| Evidence | Law of multiple proportions | Cathode ray experiments |
In 1897, Thomson discovered the electron using cathode ray tubes. This proved atoms were not indivisible. Since the whole atom was neutral, Thomson proposed a "pudding" of positive charge with negative electrons embedded like plums — or chocolate chips — inside it.
Both the cookie dough and Thomson's positive charge are continuous and spread out. The chocolate chips and electrons are discrete, embedded particles scattered throughout. It's a perfect visual match — tasty and memorable!
Click a card to jump to that model in the viewer above.
Check yourself