AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
The discovery of the electron led to the plum pudding model of the atom.…
Full specification wording
The development of the model of the atom (common content with chemistry): The discovery of the electron led to the plum pudding model of the atom. The plum pudding model suggested that the atom is a ball of positive charge with negative electrons embedded in it.
After J. J. Thomson discovered the electron in 1897, scientists needed a new model because atoms clearly contained smaller negative particles.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 3 of 10
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
After J. J. Thomson discovered the electron in 1897, scientists needed a new model because atoms clearly contained smaller negative particles. Thomson proposed the plum pudding model: a sphere of positive charge with negative electrons scattered inside it, like fruit in a pudding. The positive charge balances the negative charge, so the atom as a whole is neutral. This model was later tested by the alpha-particle scattering experiment, in which most alpha particles passed straight through gold foil but a few were deflected strongly. That result did not fit the plum pudding model and led to the nuclear model. When answering, describe the arrangement of charge and explain how the model accounted for a neutral atom.
What earns the marks
- State that the discovery of the electron led to the plum pudding model.
- Describe the atom as a ball or sphere of positive charge.
- State that negative electrons are embedded or scattered within the positive sphere.
- Explain that the positive and negative charges balance so the atom is neutral overall.
- Link the model to Thomson and to the later alpha-particle scattering evidence that replaced it.
Common mistakes and how to put them right
Saying electrons orbit the nucleus.
Put it right by stating that in the plum pudding model there is no nucleus and electrons are embedded in a positive sphere.
Saying the atom is negatively charged.
Put it right by explaining that equal positive and negative charge makes the atom neutral.
Confusing the plum pudding model with the nuclear model.
Put it right by stating that the nuclear model came later, after alpha-particle scattering results.
Exam tips
- Use the phrase ball of positive charge with electrons embedded to match the specification.
- State clearly that the overall charge is neutral because the charges balance.
- Mention that the model was replaced after alpha-particle scattering evidence.
Try the lesson
The start of the The development of the model of the atom (common content with chemistry): The discovery of the electron led to the plum pudding model of the atom. The plum pudding model suggested that the atom is a ball of positive charge with negative electrons embedded in it. lesson, made from checked teaching notes for this specification point.
Have a go first
In the plum pudding model, what is the overall charge of the ball of positive charge with the negative electrons embedded in it?
Listen
After J. J. Thomson discovered the electron in 1897, scientists needed a new model because atoms clearly contained smaller negative particles. Thomson proposed the plum pudding model: a sphere of positive charge with negative electrons scattered inside it, like fruit in a pudding. The positive charge balances the negative charge, so the atom as a whole is neutral. This model was later tested by the alpha-particle scattering experiment, in which most alpha particles passed straight through gold foil but a few were deflected strongly. That result did not fit the plum pudding model and led to the nuclear model. When answering, describe the arrangement of charge and explain how the model accounted for a neutral atom. A strong answer earns marks for these points. State that the discovery of the electron led to the plum pudding model. Describe the atom as a ball or sphere of positive charge. State that negative electrons are embedded or scattered within the positive sphere. Explain that the positive and negative charges balance so the atom is neutral overall. A common slip: Saying electrons orbit the nucleus. Instead, stating that in the plum pudding model there is no nucleus and electrons are embedded in a positive sphere. Exam tip: Use the phrase ball of positive charge with electrons embedded to match the specification.
See it
Key words
Say what each word means before you turn the card.
plum pudding model
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electron
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neutral atom
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nuclear model
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See every definition
- plum pudding model
- A model suggesting that the atom is a ball of positive charge with negative electrons embedded in it.
- electron
- A negative particle that is embedded in the ball of positive charge in the plum pudding model.
- neutral atom
- An atom in which the positive and negative charges balance, so the atom as a whole is neutral.
- nuclear model
- The model that replaced the plum pudding model after alpha-particle scattering evidence did not fit it.
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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