AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
The results from the alpha particle scattering experiment led to the…
Full specification wording
The development of the model of the atom (common content with chemistry): The results from the alpha particle scattering experiment led to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged. This nuclear model replaced the plum pudding model.
Rutherford's team fired alpha particles at thin gold foil.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 4 of 10
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Rutherford's team fired alpha particles at thin gold foil. Most passed straight through, showing atoms are mainly empty space. A small number were deflected through large angles, and a very few bounced back. This is only possible if positive charge and most mass sit in a tiny central nucleus. The plum pudding model, with negative electrons embedded in a ball of positive charge, cannot explain large deflections. So the nuclear model replaced it. To reason this through, compare each observation with each model: straight-through supports empty space; large-angle deflection needs a concentrated positive centre; bounce-back needs that centre to be massive.
What earns the marks
- Most alpha particles passed straight through the foil, which shows that most of an atom is empty space.
- A small number of alpha particles were deflected through large angles, which shows that the atom contains a concentrated region of positive charge.
- A very small number of alpha particles were deflected back towards the source, which shows that this central region is also where most of the atom's mass is concentrated.
- The nucleus is positively charged, so it repels the positively charged alpha particles that pass close to it.
- The plum pudding model could not explain the large-angle deflections, so the nuclear model replaced it.
Common mistakes and how to put them right
Saying alpha particles are attracted to the nucleus.
Put it right: State that the nucleus repels alpha particles, causing deflection.
Claiming most alpha particles were deflected.
Put it right: Link straight-through to empty space and deflection to the nucleus.
Stating the nucleus contains most of the atom's volume.
Put it right: Distinguish mass concentration from volume.
Exam tips
- Link each observation to a conclusion explicitly, for example 'most passed straight through, therefore the atom is mainly empty space'.
- Use the phrase 'concentrated positive charge' when explaining large-angle deflection, and add 'most of the mass' when explaining particles bouncing back.
- When comparing models, state one clear limitation of the plum pudding model rather than describing both models in full.
Try the lesson
The start of the The development of the model of the atom (common content with chemistry): The results from the alpha particle scattering experiment led to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged. This nuclear model replaced the plum pudding model. lesson, made from checked teaching notes for this specification point.
Have a go first
In the alpha particle scattering experiment, the great majority of the alpha particles travelled straight through the thin gold foil without changing direction. Which conclusion about the atom follows from this observation?
Listen
Rutherford's team fired alpha particles at thin gold foil. Most passed straight through, showing atoms are mainly empty space. A small number were deflected through large angles, and a very few bounced back. This is only possible if positive charge and most mass sit in a tiny central nucleus. The plum pudding model, with negative electrons embedded in a ball of positive charge, cannot explain large deflections. So the nuclear model replaced it. To reason this through, compare each observation with each model: straight-through supports empty space; large-angle deflection needs a concentrated positive centre; bounce-back needs that centre to be massive. A strong answer earns marks for these points. Most alpha particles passed straight through the foil, which shows that most of an atom is empty space. A small number of alpha particles were deflected through large angles, which shows that the atom contains a concentrated region of positive charge. A very small number of alpha particles were deflected back towards the source, which shows that this central region is also where most of the atom's mass is concentrated. The nucleus is positively charged, so it repels the positively charged alpha particles that pass close to it. A common slip: Saying alpha particles are attracted to the nucleus: they are repelled because both are positively charged. Instead, state that the nucleus repels alpha particles, causing deflection. Exam tip: Link each observation to a conclusion explicitly, for example 'most passed straight through, therefore the atom is mainly empty space'.
Key words
Say what each word means before you turn the card.
nucleus
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nuclear model
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plum pudding model
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alpha particle scattering experiment
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See every definition
- nucleus
- The centre of an atom, where the mass of the atom is concentrated and which is charged.
- nuclear model
- The model in which the mass of an atom is concentrated at the centre and the nucleus is charged.
- plum pudding model
- The model with negative electrons embedded in a ball of positive charge, which the nuclear model replaced.
- alpha particle scattering experiment
- An experiment whose results led to the conclusion that the mass of an atom was concentrated at the centre and that the nucleus was charged.
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