Year 8 Science · Unit 2 · Lesson 09
Apply Worksheet
Learning Goals
Compare two
Complete the table to compare Thomson's plum pudding model and Rutherford's nuclear model. Fill in both columns using what you know from the lesson.
| Feature | Thomson's Plum Pudding Model | Rutherford's Nuclear Model |
|---|---|---|
| Location of electrons | ||
| Location of positive charge | ||
| Is a nucleus present? | ||
| What experiment supported it | ||
| One limitation of the model |
Scenario
Rutherford expected all alpha particles to pass through the gold foil with only slight deflections, based on Thomson's plum pudding model, because if positive charge was spread evenly throughout the atom, there would be nothing dense enough to bounce particles back. Instead, about 1 in 8,000 particles bounced almost straight back. This completely surprised Rutherford and his team.
(a) Predict: Why did this unexpected result force scientists to reject the plum pudding model? Explain what the result showed that the plum pudding model could not account for.
(b) Explain: What did the bouncing-back of alpha particles reveal about atomic structure? What must be true about the centre of an atom for this result to occur?
1. Both Thomson's and Rutherford's experiments produced surprising results that changed how scientists thought about the atom. Choose one of these experiments and explain how the evidence it produced led to a new atomic model.
2. Bohr's model added electron shells to Rutherford's nuclear model. What problem with the nuclear model did Bohr's shells help to explain? (Hint: think about what electrons were observed to absorb and emit.)
Wrap Up
In one sentence, what was the main idea of this lesson?