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Nuclear Decay

Nuclear transformation equations and nuclide notation

  • 3 things to know
  • Component 3

Overview

Recall questions on nuclide notation and what each number means, the changes in nucleon and proton number in alpha, beta-minus, beta-plus and gamma emission, writing balanced nuclear equations for named decays, and checking both numbers balance.

What you need to know

Answer each one before you reveal it.

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Key term

In the notation used for nuclides, what do the two numbers written before the chemical symbol represent?

Key term

Write the nuclear equation for the α decay of ²²⁶₈₈Ra.

Key term

How do the nucleon number and the proton number change in an α decay?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    In the notation used for nuclides, what do the two numbers written before the chemical symbol represent?

    Model answer

    The upper number is the nucleon number A, the total number of protons and neutrons. The lower number is the proton number Z, the number of protons.

  2. 2

    How many neutrons does a nuclide of nucleon number A and proton number Z contain?

    Model answer

    It contains A − Z neutrons. The nucleon number counts protons and neutrons together, so taking away the protons leaves the neutrons.

  3. 3

    Give the numbers of protons and neutrons in ²³⁸₉₂U.

    Model answer

    It has 92 protons and 146 neutrons. Subtracting 92 from 238 gives the neutron count.

  4. 4

    Write the nuclear equation for the α decay of ²²⁶₈₈Ra.

    Model answer

    The equation is ²²⁶₈₈Ra → ²²²₈₆Rn + ⁴₂He. The nucleon number falls by 4 and the proton number falls by 2.

  5. 5

    How do the nucleon number and the proton number change in an α decay?

    Model answer

    The nucleon number falls by 4 and the proton number falls by 2. The nuclide therefore moves two places back in the periodic table.

  6. 6

    Write the nuclear equation for the β⁻ decay of ¹⁴₆C.

    Model answer

    The equation is ¹⁴₆C → ¹⁴₇N + ⁰₋₁e + ν̄ₑ. The nucleon number is unchanged and the proton number rises by one.

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