AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
The radius of a nucleus is less than 1/10 000 of the radius of an atom.…
Full specification wording
The structure of an atom: The radius of a nucleus is less than 1/10 000 of the radius of an atom. Most of the mass of an atom is concentrated in the nucleus.
An atom has a radius of roughly 1 × 10⁻¹⁰ m, while its nucleus is smaller than 1 × 10⁻¹⁴ m, so the nucleus occupies less than one ten-thousandth of the atomic radius.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 2 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
An atom has a radius of roughly 1 × 10⁻¹⁰ m, while its nucleus is smaller than 1 × 10⁻¹⁴ m, so the nucleus occupies less than one ten-thousandth of the atomic radius. Scaled up, if an atom were a sports stadium the nucleus would be a pea at the centre, and everything else is empty space through which the electrons move. Despite that tiny size, the nucleus holds nearly all the mass, because protons and neutrons are each about two thousand times heavier than an electron. Alpha particle scattering supplies the evidence for both claims: most alpha particles passed straight through the foil, but a few rebounded from something small, massive and positively charged.
What earns the marks
- The radius of the nucleus being less than 1/10 000 of the radius of the atom.
- Quoting about 1 × 10⁻¹⁰ m for the atom and about 1 × 10⁻¹⁴ m or smaller for the nucleus.
- Stating that the mass of the atom is concentrated in the nucleus.
- Stating that most of the atom is empty space.
Common mistakes and how to put them right
Quoting 1/10 000 as a ratio of masses rather than of radii.
Giving the nucleus a radius of 10⁻¹⁰ m, which is the size of the whole atom.
Saying the electrons account for most of the mass because there are several of them.
Claiming the nucleus is massive because it is large.
Exam tips
- Learn the two orders of magnitude, 10⁻¹⁰ m and 10⁻¹⁴ m; comparison questions often just want these.
- Answer mass questions with the phrase concentrated in the nucleus, which is the wording the mark scheme uses.
- If the question asks about the atom being mostly empty space, link it to alpha particles passing straight through.
Try the lesson
The start of the The structure of an atom: The radius of a nucleus is less than 1/10 000 of the radius of an atom. Most of the mass of an atom is concentrated in the nucleus. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement about the nucleus of an atom is correct?
Listen
An atom has a radius of roughly 1 × 10⁻¹⁰ m, while its nucleus is smaller than 1 × 10⁻¹⁴ m, so the nucleus occupies less than one ten-thousandth of the atomic radius. Scaled up, if an atom were a sports stadium the nucleus would be a pea at the centre, and everything else is empty space through which the electrons move. Despite that tiny size, the nucleus holds nearly all the mass, because protons and neutrons are each about two thousand times heavier than an electron. Alpha particle scattering supplies the evidence for both claims: most alpha particles passed straight through the foil, but a few rebounded from something small, massive and positively charged. A strong answer earns marks for these points. the radius of the nucleus being less than 1/10 000 of the radius of the atom. quoting about 1 × 10⁻¹⁰ m for the atom and about 1 × 10⁻¹⁴ m or smaller for the nucleus. stating that the mass of the atom is concentrated in the nucleus. stating that most of the atom is empty space. Exam tip: Learn the two orders of magnitude, 10⁻¹⁰ m and 10⁻¹⁴ m; comparison questions often just want these.
Key words
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nuclear radius
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concentration of mass
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empty space
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orders of magnitude
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See every definition
- nuclear radius
- The radius of a nucleus is less than 1/10 000 of the radius of an atom.
- concentration of mass
- Most of the mass of an atom is concentrated in the nucleus.
- empty space
- Everything else in the atom is empty space through which the electrons move.
- orders of magnitude
- The two orders of magnitude to learn are 10⁻¹⁰ m and 10⁻¹⁴ m.
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