S4.6.2 For the adult
How the model of the atom changed
How can you find out what is inside something you cannot see?
What this chapter teaches
The model of the atom changed as new evidence came in: Dalton, Thomson, Rutherford with Geiger and Marsden, Bohr, then Chadwick. The gold foil results showed a tiny, dense, positive nucleus and mostly empty space.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why did most alpha particles pass straight through the gold foil?
- What did the few that bounced back tell scientists?
- Why do we still use the Bohr model if it is not what an atom really looks like?
After the chapter, the learner can
- Describe how the atom model changed from Dalton to Bohr
- Explain how the gold foil experiment showed a tiny nucleus
What they copy into their notebook
A model explains the evidence and changes when new evidence does not fit. Gold foil: most alpha particles pass through, a few bounce back. So atoms are mostly empty space with a tiny, dense, positive nucleus.