AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
The development of the model of the atom (common content with physics): the difference between the plum pudding model of the atom and the nuclear model of the atom.
The plum pudding model pictured the atom as a ball of positive charge with negative electrons embedded in it, rather like fruit in a pudding.
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The plum pudding model pictured the atom as a ball of positive charge with negative electrons embedded in it, rather like fruit in a pudding. The nuclear model replaced this with a tiny, dense, positively charged nucleus at the centre, surrounded by mostly empty space in which electrons orbit. The key differences are the distribution of positive charge and the amount of empty space. In the plum pudding model positive charge is spread throughout; in the nuclear model it is concentrated in a very small central nucleus. This change followed the scattering experiment evidence.
What earns the marks
- Describe the plum pudding model as a sphere of positive charge with electrons embedded in it.
- Describe the nuclear model as a small, dense, positive nucleus with electrons outside it.
- Contrast the distribution of positive charge: spread out versus concentrated in the nucleus.
- Contrast the amount of empty space: the nuclear model has mostly empty space, the plum pudding model does not.
- Link the change to evidence from the alpha-particle scattering experiment.
Common mistakes and how to put them right
Placing electrons inside the nucleus.
Put it right by stating electrons are outside the nucleus in the nuclear model.
Saying the plum pudding model has a nucleus.
Put it right by noting positive charge is spread throughout the atom.
Confusing the two models' names.
Put it right by linking 'pudding' to embedded electrons and 'nuclear' to a central nucleus.
Exam tips
- Use a labelled diagram or a clear sentence to contrast the two models side by side.
- Mention both the position of positive charge and the presence of empty space for full comparison.
- Keep the answer focused on differences, not a full history of atomic theory.
Try the lesson
The start of the The development of the model of the atom (common content with physics): the difference between the plum pudding model of the atom and the nuclear model of the atom. lesson, made from checked teaching notes for this specification point.
Have a go first
In the plum pudding model of the atom, how was the positive charge described?
Listen
The plum pudding model pictured the atom as a ball of positive charge with negative electrons embedded in it, rather like fruit in a pudding. The nuclear model replaced this with a tiny, dense, positively charged nucleus at the centre, surrounded by mostly empty space in which electrons orbit. The key differences are the distribution of positive charge and the amount of empty space. In the plum pudding model positive charge is spread throughout; in the nuclear model it is concentrated in a very small central nucleus. This change followed the scattering experiment evidence. A strong answer earns marks for these points. Describe the plum pudding model as a sphere of positive charge with electrons embedded in it. Describe the nuclear model as a small, dense, positive nucleus with electrons outside it. Contrast the distribution of positive charge: spread out versus concentrated in the nucleus. Contrast the amount of empty space: the nuclear model has mostly empty space, the plum pudding model does not. A common slip: Placing electrons inside the nucleus. Instead, stating electrons are outside the nucleus in the nuclear model. Exam tip: Use a labelled diagram or a clear sentence to contrast the two models side by side.
See it
Key words
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Atomic models
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Charge distribution
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Structure of the atom
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Development of scientific ideas
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See every definition
- Atomic models
- The plum pudding model pictures a sphere of positive charge with electrons embedded in it, while the nuclear model has a small, dense, positive nucleus with electrons outside it.
- Charge distribution
- In the plum pudding model positive charge is spread throughout, whereas in the nuclear model it is concentrated in a very small central nucleus.
- Structure of the atom
- The nuclear model has a tiny, dense, positively charged nucleus at the centre, surrounded by mostly empty space in which electrons orbit.
- Development of scientific ideas
- The change from the plum pudding model to the nuclear model followed the scattering experiment evidence.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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