AQA · GCSE · Physics

    Course version: 8463 · Version from Sept 2016

    The emission of a gamma ray does not cause the mass or the charge of the…

    Full specification wording

    Nuclear equations: The emission of a gamma ray does not cause the mass or the charge of the nucleus to change.

    A gamma ray is electromagnetic radiation, not a particle of matter.

    Checked against the AQA 8463 specification (opens in a new tab) on .

    • Point 6 of 6
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    A gamma ray is electromagnetic radiation, not a particle of matter. It has no mass and no charge, so when a nucleus emits one it loses no nucleons and no protons: the mass number stays the same and the atomic number stays the same, and the nucleus remains the same element. What changes is energy. The nucleus was left in an excited, higher-energy arrangement, usually just after emitting an alpha or a beta particle, and emitting the gamma ray carries that surplus energy away and leaves the nucleus more stable. In a balanced equation a gamma ray therefore contributes 0 to the mass number total and 0 to the atomic number total.

    What earns the marks

    • Stating that the mass number of the nucleus is unchanged.
    • Stating that the atomic number, and so the charge, is unchanged.
    • Explaining this because a gamma ray has no mass and no charge.
    • Stating that the nucleus loses energy and becomes more stable.

    Common mistakes and how to put them right

    • Reducing the mass number because energy has left the nucleus.

    • Saying the nucleus becomes a different element after gamma emission.

    • Describing a gamma ray as a particle emitted from the electron shells.

    • Assuming a nucleus that emits gamma must also emit an alpha or beta particle in the same step.

    Exam tips

    • Answer in two halves: both numbers unchanged, and why, which is no mass and no charge.
    • Mention that gamma emission still makes the nucleus more stable, since it loses energy.
    • In an equation, write 0 above and 0 below the gamma symbol so the balance is obvious.

    Try the lesson

    The start of the Nuclear equations: The emission of a gamma ray does not cause the mass or the charge of the nucleus to change. lesson, made from checked teaching notes for this specification point.

    Have a go first

    A nucleus emits a gamma ray. What happens to the mass number and the atomic number of the nucleus?

    Listen

    A gamma ray is electromagnetic radiation, not a particle of matter. It has no mass and no charge, so when a nucleus emits one it loses no nucleons and no protons: the mass number stays the same and the atomic number stays the same, and the nucleus remains the same element. What changes is energy. The nucleus was left in an excited, higher-energy arrangement, usually just after emitting an alpha or a beta particle, and emitting the gamma ray carries that surplus energy away and leaves the nucleus more stable. In a balanced equation a gamma ray therefore contributes 0 to the mass number total and 0 to the atomic number total. A strong answer earns marks for these points. stating that the mass number of the nucleus is unchanged. stating that the atomic number, and so the charge, is unchanged. explaining this because a gamma ray has no mass and no charge. stating that the nucleus loses energy and becomes more stable. Exam tip: Answer in two halves: both numbers unchanged, and why, which is no mass and no charge.

    See it

    A top-down flowchart. The first box reads 'Nucleus in excited, higher-energy state' and points to a second box, 'Emits a gamma ray'. That box points to a third box, 'Gamma ray has no mass and no charge'. The third box branches into two boxes: 'Mass number unchanged' and 'Atomic number and charge unchanged'. Both of these point to a single box, 'Nucleus remains the same element'. The 'Emits a gamma ray' box also points separately to a final box, 'Nucleus loses energy and becomes more stable'.
    It shows that emitting a gamma ray leaves the mass number and atomic number unchanged because the gamma ray has no mass and no charge, while the nucleus loses energy and becomes more stable.

    Key words

    Say what each word means before you turn the card.

    gamma emission

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    no change of mass number

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    no change of charge

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    loss of energy

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    See every definition
    gamma emission
    The emission of a gamma ray, which does not cause the mass or the charge of the nucleus to change.
    no change of mass number
    The mass number stays the same because a gamma ray has no mass and no nucleons are lost.
    no change of charge
    The atomic number, and so the charge, is unchanged because a gamma ray has no charge.
    loss of energy
    The nucleus was left in an excited, higher-energy arrangement and emitting the gamma ray carries that surplus energy away, leaving the nucleus more stable.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. The first box reads 'Nucleus in excited, higher-energy state' and points to a second box, 'Emits a gamma ray'. That box points to a third box, 'Gamma ray has no mass and no charge'. The third box branches into two boxes: 'Mass number unchanged' and 'Atomic number and charge unchanged'. Both of these point to a single box, 'Nucleus remains the same element'. The 'Emits a gamma ray' box also points separately to a final box, 'Nucleus loses energy and becomes more stable'.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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