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Practise 30 exam-style questions on The development of the model of the atom for AQA GCSE Chemistry. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Name the model of the atom that replaced the plum pudding model.
The nuclear model.
The results of the alpha particle scattering experiment led to the nuclear model, which replaced the plum pudding model. Bohr later adapted the nuclear model - he did not replace the plum pudding model.
the nuclear model
allow Rutherford's model; do not accept Bohr model
Suggest two reasons why other scientists accepted the nuclear model of the atom.
Other scientists repeated the alpha particle scattering experiment and got the same results. The nuclear model explained all of these results, including the alpha particles that bounced back, which the plum pudding model could not explain.
A new model is accepted when it explains the evidence better than the old one and when other scientists can check and reproduce the results. Further experiments that support the model strengthen it.
other scientists repeated the experiment and got the same results / the results were reproducible
max 2
the nuclear model explained all the results of the scattering experiment (which the plum pudding model could not)
the results were published / peer reviewed / checked by other scientists
later evidence supported it (e.g. Bohr's calculations agreed with experimental observations)
Alpha particles are positively charged. In the alpha particle scattering experiment, predict what would happen to an alpha particle in each of these situations:
- it travels directly towards a gold nucleus
- it passes close to a gold nucleus
- it passes far away from any nucleus
An alpha particle travelling directly towards a nucleus is strongly repelled and bounces back. One passing close to a nucleus is repelled to one side and deflected. One passing far from any nucleus goes straight through without being deflected.
The positive nucleus repels the positive alpha particles, and the repulsion is stronger the closer they get. Because the nucleus is so small, most alpha particles are far from any nucleus and go straight through.
directly towards a nucleus: it bounces back
allow it is repelled back the way it came / deflected through a very large angle
close to a nucleus: it is deflected / changes direction (away from the nucleus)
allow it is repelled to one side
far from any nucleus: it passes straight through (undeflected)
A student says: "The plum pudding model turned out to be wrong, so it was a waste of time."
Evaluate the student's statement.
I disagree with the student. When the plum pudding model was suggested it explained the evidence available at the time: atoms contain negative electrons but are neutral overall. It was an improvement on the idea of indivisible spheres. It also made predictions that could be tested, and testing it in the alpha particle scattering experiment produced new evidence that led to the nuclear model. Science develops by proposing models, testing them and replacing them when new evidence is found, so the plum pudding model was an important step, not a waste of time.
An 'evaluate' question needs points on both sides or reasons for a view, followed by a judgement. Models that are later replaced are still useful because they explain current evidence and lead to the experiments that improve our understanding.
the plum pudding model explained the evidence available at the time (atoms contain electrons and are neutral)
max 4; max 3 if no judgement about the statement is given
it was an improvement on the indivisible sphere model / showed that atoms contain smaller particles
it made predictions that could be tested (e.g. by the alpha scattering experiment)
testing it produced new evidence that led to the nuclear model
judgement: the statement is wrong because science develops by testing models and replacing them when new evidence is found
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