AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
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.
Geiger and Marsden fired alpha particles, which are positively charged and relatively heavy, at a very thin gold foil and recorded where they went.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 5 of 12
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Geiger and Marsden fired alpha particles, which are positively charged and relatively heavy, at a very thin gold foil and recorded where they went. Three results mattered. Most passed straight through undeflected, so the atom must be mostly empty space. A small number were deflected through large angles, so somewhere inside there is a concentration of positive charge repelling them. A very few bounced almost straight back, which can only happen if they met something both positively charged and far more massive than themselves. Put together, the atom has a tiny central nucleus that is positively charged and holds almost all the mass, with the electrons far outside it.
What earns the marks
- Most alpha particles passing straight through, showing the atom is mostly empty space.
- Some being deflected through large angles, showing a concentration of positive charge.
- A very few rebounding, showing the mass of the atom is concentrated in the nucleus.
- Stating that the nucleus is charged and very small compared with the whole atom.
Common mistakes and how to put them right
Saying the alpha particles were repelled by the electrons.
Pairing the observations with the wrong conclusions, such as using the rebounds to argue for empty space.
Claiming the experiment provided the evidence for neutrons.
Forgetting that the alpha particle is positive, so the deflection is caused by repulsion.
Exam tips
- Answer in pairs: one observation then the conclusion it supports, repeated for each result.
- Use the word repelled and say both the alpha particle and the nucleus are positive.
- Learn the mark scheme phrase, the mass of the atom is concentrated in the nucleus.
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. lesson, made from checked teaching notes for this specification point.
Have a go first
What conclusion about the mass of an atom was drawn from the results of the alpha particle scattering experiment?
Listen
Geiger and Marsden fired alpha particles, which are positively charged and relatively heavy, at a very thin gold foil and recorded where they went. Three results mattered. Most passed straight through undeflected, so the atom must be mostly empty space. A small number were deflected through large angles, so somewhere inside there is a concentration of positive charge repelling them. A very few bounced almost straight back, which can only happen if they met something both positively charged and far more massive than themselves. Put together, the atom has a tiny central nucleus that is positively charged and holds almost all the mass, with the electrons far outside it. A strong answer earns marks for these points. most alpha particles passing straight through, showing the atom is mostly empty space. some being deflected through large angles, showing a concentration of positive charge. a very few rebounding, showing the mass of the atom is concentrated in the nucleus. stating that the nucleus is charged and very small compared with the whole atom. Exam tip: Answer in pairs: one observation then the conclusion it supports, repeated for each result.
Key words
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alpha particle scattering
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gold foil
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empty space
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concentrated positive charge
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See every definition
- alpha particle scattering
- Firing alpha particles, which are positively charged and relatively heavy, at a very thin gold foil and recording where they went.
- gold foil
- The very thin material at which the alpha particles were fired in the experiment.
- empty space
- What the atom must be mostly made of, because most alpha particles passed straight through undeflected.
- concentrated positive charge
- What is somewhere inside the atom, repelling the small number of alpha particles that were deflected through large angles.
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