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Radioactivity

Effects of decay on atomic number and mass number

  • 2 things to know
  • Paper 1

Overview

How alpha, beta-minus, beta-plus, gamma and neutron emission each change mass number and atomic number, worked examples, and why a gamma ray often follows another decay.

What you need to know

Answer each one before you reveal it.

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Key term

What happens to the mass number and the atomic number when a nucleus emits an alpha particle?

Key term

What happens to the mass number and the atomic number when a nucleus emits a β⁻ particle?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What happens to the mass number and the atomic number when a nucleus emits an alpha particle?

    Model answer

    The mass number falls by 4 and the atomic number falls by 2.

  2. 2

    What happens to the mass number and the atomic number when a nucleus emits a β⁻ particle?

    Model answer

    The mass number is unchanged and the atomic number rises by 1.

  3. 3

    What happens to the mass number and the atomic number when a nucleus emits a β⁺ particle?

    Model answer

    The mass number is unchanged and the atomic number falls by 1.

  4. 4

    What happens to the mass number and the atomic number when a nucleus emits a gamma ray?

    Model answer

    Both are unchanged, because gamma emission removes only energy from the nucleus.

  5. 5

    What happens to the mass number and the atomic number when a nucleus emits a neutron?

    Model answer

    The mass number falls by 1 and the atomic number is unchanged.

  6. 6

    A nucleus of mass number 226 and atomic number 88 emits an alpha particle. State the mass number and atomic number of the nucleus formed.

    Model answer

    The new nucleus has mass number 222 and atomic number 86.

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