AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Some atomic nuclei are unstable. The nucleus gives out radiation as it…
Full specification wording
Radioactive decay and nuclear radiation: Some atomic nuclei are unstable. The nucleus gives out radiation as it changes to become more stable. This is a random process called radioactive decay.
A nucleus with an unsuitable balance of protons and neutrons is unstable, and at some point it emits radiation and becomes more stable.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 1 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A nucleus with an unsuitable balance of protons and neutrons is unstable, and at some point it emits radiation and becomes more stable. It is the nucleus that decays, not the electrons and not the atom as a chemical object, which is why nothing you do to the outside of the material changes the rate: heating it, cooling it, dissolving it or squeezing it all leave the decay untouched. Decay is random in a precise sense. You cannot predict which nucleus in a sample will decay next, and you cannot predict when any particular nucleus will decay. Only across very large numbers of nuclei does a reliable average emerge, and that average is what half-life describes.
What earns the marks
- Stating that some nuclei are unstable and emit radiation to become more stable.
- Stating that it cannot be predicted which nucleus will decay next.
- Stating that it cannot be predicted when a given nucleus will decay.
- Stating that the decay rate is unaffected by external conditions such as temperature.
Common mistakes and how to put them right
Saying the atom decays rather than the nucleus.
Claiming decay can be speeded up by heating or by a chemical reaction.
Reading random as meaning there is no pattern at all, even across a large sample.
Saying the nucleus becomes unstable as a result of emitting radiation, rather than before it.
Exam tips
- Give both halves of randomness, which nucleus and when, because they are usually separate marks.
- Say nucleus, not atom, throughout any answer about decay.
- A dice analogy is accepted: you cannot say which dice will show a six, or on which throw.
Try the lesson
The start of the Radioactive decay and nuclear radiation: Some atomic nuclei are unstable. The nucleus gives out radiation as it changes to become more stable. This is a random process called radioactive decay. lesson, made from checked teaching notes for this specification point.
Have a go first
What name is given to the random process in which an unstable nucleus gives out radiation and becomes more stable?
Listen
A nucleus with an unsuitable balance of protons and neutrons is unstable, and at some point it emits radiation and becomes more stable. It is the nucleus that decays, not the electrons and not the atom as a chemical object, which is why nothing you do to the outside of the material changes the rate: heating it, cooling it, dissolving it or squeezing it all leave the decay untouched. Decay is random in a precise sense. You cannot predict which nucleus in a sample will decay next, and you cannot predict when any particular nucleus will decay. Only across very large numbers of nuclei does a reliable average emerge, and that average is what half-life describes. A strong answer earns marks for these points. stating that some nuclei are unstable and emit radiation to become more stable. stating that it cannot be predicted which nucleus will decay next. stating that it cannot be predicted when a given nucleus will decay. stating that the decay rate is unaffected by external conditions such as temperature. Exam tip: Give both halves of randomness, which nucleus and when, because they are usually separate marks.
See it
Key words
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unstable nuclei
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radioactive decay
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randomness
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independence from conditions
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See every definition
- unstable nuclei
- Some atomic nuclei are unstable and give out radiation as they change to become more stable.
- radioactive decay
- A random process in which an unstable nucleus gives out radiation as it changes to become more stable.
- randomness
- You cannot predict which nucleus in a sample will decay next, and you cannot predict when any particular nucleus will decay.
- independence from conditions
- Heating, cooling, dissolving or squeezing the material all leave the decay untouched, so nothing done to the outside changes the rate.
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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