The table shows some discoveries that changed scientists' ideas about atoms.
| Year | Scientist(s) | Evidence or idea |
|---|---|---|
| 1803 | Dalton | Elements always combine in fixed amounts. He suggested that atoms are tiny solid spheres. |
| 1897 | Thomson | Found tiny negative particles that are much lighter than atoms. |
| 1909 | Geiger and Marsden | Fired positive alpha particles at very thin gold foil. Most went straight through. A few were deflected. A very small number bounced back. |
| 1913 | Bohr | Used calculations and the light given out by atoms. Suggested that electrons can only be at certain distances from the nucleus. |
| 1932 | Chadwick | Found particles in the nucleus with no charge and about the same mass as a proton. |
Which scientist was the first to show that atoms contain smaller particles?
Before Rutherford's nuclear model was accepted, other scientists repeated Geiger and Marsden's experiment.
Suggest why.
Describe how and why the model of the atom changed between 1803 and 1932.
Use the information in the table.
51 exam-style questions on OCR GCSE Chemistry 1.2 Atomic structure, covering 1.2.1 Development of the atomic model, 1.2.2 The nuclear model and the size of atoms, and 1.2.3 Subatomic particles in atoms and ions. Each one has a worked solution and a mark scheme showing where the marks go.