AQA · A-Level · Physics
Course version: 7408 · Version from Sept 2016
Appreciation of how knowledge and understanding of the structure of the…
Full specification wording
Rutherford scattering (A-level only): Appreciation of how knowledge and understanding of the structure of the nucleus has changed over time.
Ideas about the nucleus have developed as new evidence and techniques appeared.
Checked against the AQA 7408 specification (opens in a new tab) on .
- Point 2 of 8
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Ideas about the nucleus have developed as new evidence and techniques appeared. Thomson's plum-pudding model pictured positive charge spread throughout the atom with electrons embedded in it. Rutherford's alpha-scattering results showed that positive charge and most mass are concentrated in a tiny nucleus, so the model was replaced. Later work showed the nucleus contains protons and neutrons, and scattering experiments revealed that protons and neutrons are themselves made of quarks. The sequence shows that models are provisional: a model survives while it explains the evidence, and is modified or replaced when new evidence conflicts with it.
What earns the marks
- Thomson's plum-pudding model described positive charge spread throughout the atom with electrons embedded in it.
- Rutherford's alpha-scattering evidence showed a tiny, dense, positively charged nucleus, replacing the plum-pudding model.
- The discovery of the proton and the neutron established that the nucleus contains both types of nucleon.
- Deep inelastic scattering experiments provided evidence that protons and neutrons contain quarks.
- Each change followed new experimental evidence that the previous model could not explain.
- Scientific models are provisional and are refined or replaced as evidence and techniques improve.
Common mistakes and how to put them right
Presenting the plum-pudding model as simply wrong from the start.
Put it right: The error is ignoring that it was a reasonable model for the evidence then available.
Saying Rutherford discovered the electron.
Put it right: The error is confusing Rutherford's nuclear model with Thomson's earlier identification of the electron.
Claiming the nucleus has always been understood as protons and neutrons.
Put it right: The error is ignoring the later discovery of the neutron and of quarks.
Exam tips
- Sequence the models in time and name the key evidence that prompted each change.
- Use words such as 'evidence', 'model' and 'replaced' to show how understanding developed.
- Avoid implying that the current model is final; describe it as the best explanation of current evidence.
Try the lesson
The start of the Rutherford scattering (A-level only): Appreciation of how knowledge and understanding of the structure of the nucleus has changed over time. lesson, made from checked teaching notes for this specification point.
Have a go first
Before Rutherford's scattering experiment, the prevailing model of the atom was the plum pudding model. What did this model propose?
Listen
Ideas about the nucleus have developed as new evidence and techniques appeared. Thomson's plum-pudding model pictured positive charge spread throughout the atom with electrons embedded in it. Rutherford's alpha-scattering results showed that positive charge and most mass are concentrated in a tiny nucleus, so the model was replaced. Later work showed the nucleus contains protons and neutrons, and scattering experiments revealed that protons and neutrons are themselves made of quarks. The sequence shows that models are provisional: a model survives while it explains the evidence, and is modified or replaced when new evidence conflicts with it. A strong answer earns marks for these points. Thomson's plum-pudding model described positive charge spread throughout the atom with electrons embedded in it. Rutherford's alpha-scattering evidence showed a tiny, dense, positively charged nucleus, replacing the plum-pudding model. The discovery of the proton and the neutron established that the nucleus contains both types of nucleon. Deep inelastic scattering experiments provided evidence that protons and neutrons contain quarks. Exam tip: Sequence the models in time and name the key evidence that prompted each change.
Key words
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Development of scientific models
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Role of experimental evidence
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Atomic and nuclear structure
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Provisional nature of science
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See every definition
- Development of scientific models
- Ideas about the nucleus have developed as new evidence and techniques appeared, with each change following new experimental evidence that the previous model could not explain.
- Role of experimental evidence
- Rutherford's alpha-scattering results showed that positive charge and most mass are concentrated in a tiny nucleus, so the plum-pudding model was replaced.
- Atomic and nuclear structure
- Later work showed the nucleus contains protons and neutrons, and scattering experiments revealed that protons and neutrons are themselves made of quarks.
- Provisional nature of science
- A model survives while it explains the evidence, and is modified or replaced when new evidence conflicts with it.
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