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Radioactivity

Balancing nuclear equations

  • 3 things to know
  • Paper 5

Overview

Balancing mass number and charge in a nuclear equation, finding an unknown nucleus or particle, and how β⁻ particles and positrons are written.

What you need to know

Answer each one before you reveal it.

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Key term

What two quantities must balance on the two sides of a nuclear equation?

Key term

In the decay ²³⁸₉₂U → X + ⁴₂He, state the mass number and atomic number of nucleus X.

Key term

In the decay ⁹⁰₃₈Sr → X + ⁰₋₁e, state the mass number and atomic number of nucleus X.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What two quantities must balance on the two sides of a nuclear equation?

    Model answer

    The total mass number and the total charge.

  2. 2

    In the decay ²³⁸₉₂U → X + ⁴₂He, state the mass number and atomic number of nucleus X.

    Model answer

    X has mass number 234 and atomic number 90.

  3. 3

    In the decay ⁹⁰₃₈Sr → X + ⁰₋₁e, state the mass number and atomic number of nucleus X.

    Model answer

    X has mass number 90 and atomic number 39.

  4. 4

    How is a β⁻ particle written in a nuclear equation?

    Model answer

    It is written as ⁰₋₁e, with a mass number of 0 and a charge of −1.

  5. 5

    How is a positron written in a nuclear equation?

    Model answer

    It is written as ⁰₊₁e, with a mass number of 0 and a charge of +1.

  6. 6

    In the decay ¹⁸₉F → ¹⁸₈O + X, what particle is X?

    Model answer

    X is a positron.

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