AQA · GCSE · Physics

    Course version: 8463 · Version from Sept 2016

    This is limited to balancing the atomic numbers and mass numbers.

    Full specification wording

    Nuclear equations: This is limited to balancing the atomic numbers and mass numbers.

    The examinable skill is arithmetic, not nuclear theory.

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

    • Point 5 of 6
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    The examinable skill is arithmetic, not nuclear theory. You balance two totals and nothing else: the mass numbers across the equation and the atomic numbers across the equation. Neutrinos, binding energy, decay chains and the details of what holds a nucleus together are all outside this specification. Treat the emitted particle as a full member of the totals, with its own two numbers, ⁴₂He or ⁰₋₁e, and remember that the -1 on a beta particle has to be included when the atomic numbers are added. A gamma ray contributes zero to both totals, so it never changes the balance of an equation it appears in.

    What earns the marks

    • The total mass number on the right equalling the mass number on the left.
    • The total atomic number on the right equalling the atomic number on the left.
    • Including the emitted particle's own numbers in both totals.
    • A completed equation with every missing value filled in.

    Common mistakes and how to put them right

    • Adding a neutrino or other particle that the specification does not require.

    • Balancing the equation by altering the original nucleus instead of the products.

    • Ignoring the -1 on a beta particle when adding the atomic numbers.

    • Subtracting the atomic number from the mass number by mistake while checking.

    Exam tips

    • Two totals, two checks; do them both before moving on.
    • Never change a number the question has already printed.
    • If a gamma ray appears, write 0 above and 0 below it so the totals stay clear.

    Try the lesson

    The start of the Nuclear equations: This is limited to balancing the atomic numbers and mass numbers. lesson, made from checked teaching notes for this specification point.

    Have a go first

    A nucleus of radon-222 emits an alpha particle. The nuclear equation is shown. ²²²₈₆Rn → ²¹⁸₈₄Po + ⁴₂He. Which numbers are balanced in this equation?

    Listen

    The examinable skill is arithmetic, not nuclear theory. You balance two totals and nothing else: the mass numbers across the equation and the atomic numbers across the equation. Neutrinos, binding energy, decay chains and the details of what holds a nucleus together are all outside this specification. Treat the emitted particle as a full member of the totals, with its own two numbers, ⁴₂He or ⁰₋₁e, and remember that the -1 on a beta particle has to be included when the atomic numbers are added. A gamma ray contributes zero to both totals, so it never changes the balance of an equation it appears in. A strong answer earns marks for these points. the total mass number on the right equalling the mass number on the left. the total atomic number on the right equalling the atomic number on the left. including the emitted particle's own numbers in both totals. a completed equation with every missing value filled in. Exam tip: Two totals, two checks; do them both before moving on.

    See it

    A flowchart running top to bottom. At the top is a node labelled 'Nuclear equation to balance', which branches to two nodes: 'Total mass numbers on the left' and 'Total atomic numbers on the left'. The mass-number node leads to 'Total mass numbers on the right', which leads to 'Mass numbers balance'. The atomic-number node leads to 'Total atomic numbers on the right', which leads to 'Atomic numbers balance'. Three further nodes feed into the right-hand totals: 'Emitted particle: include its own two numbers' points to both right-hand totals; 'Beta particle: include the -1 in the atomic numbers' points to the atomic-number total; and 'Gamma ray: contributes zero to both totals' points to both right-hand totals.
    Shows the two totals that must balance in a nuclear equation and how the emitted particle's numbers, including the -1 of a beta particle and the zero of a gamma ray, feed into them.

    Key words

    Say what each word means before you turn the card.

    balancing equations

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    two conservation totals

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    emitted particle numbers

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    scope of the specification

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    See every definition
    balancing equations
    Limited to balancing the atomic numbers and mass numbers, with the mass numbers across the equation and the atomic numbers across the equation.
    two conservation totals
    The mass numbers across the equation and the atomic numbers across the equation, which are the two totals you balance and nothing else.
    emitted particle numbers
    The emitted particle is treated as a full member of the totals, with its own two numbers, and the -1 on a beta particle has to be included when the atomic numbers are added.
    scope of the specification
    Neutrinos, binding energy, decay chains and the details of what holds a nucleus together are all outside this specification.

    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 flowchart running top to bottom. At the top is a node labelled 'Nuclear equation to balance', which branches to two nodes: 'Total mass numbers on the left' and 'Total atomic numbers on the left'. The mass-number node leads to 'Total mass numbers on the right', which leads to 'Mass numbers balance'. The atomic-number node leads to 'Total atomic numbers on the right', which leads to 'Atomic numbers balance'. Three further nodes feed into the right-hand totals: 'Emitted particle: include its own two numbers' points to both right-hand totals; 'Beta particle: include the -1 in the atomic numbers' points to the atomic-number total; and 'Gamma ray: contributes zero to both totals' points to both right-hand totals.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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