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Atomic and Nuclear Decay Worksheet

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Atomic and Nuclear Decay Worksheet

A research team is checking how unstable nuclei change as they decay. Use nuclide notation, conservation of nucleon number A and proton number Z, and the reference below to solve each task. In β⁻ decay, an electron and an electron antineutrino are emitted; the antineutrino is omitted from the simplified equations in this worksheet.

Reference: what changes?

α emission: A decreases by 4 and Z decreases by 2. β⁻ emission: A is unchanged and Z increases by 1. γ emission: A and Z are unchanged; an excited nucleus releases energy. Check that A and Z balance on both sides of every nuclear equation.

Decode the emissions

For each equation, identify the decay mode and explain the evidence using the changes in A and Z.

1.A detector records ²²⁶₈₈Ra → ²²²₈₆Rn + ⁴₂He. Identify the decay mode and state the changes in A and Z.

2.A sample undergoes ³²₁₅P → ³²₁₆S + ⁰₋₁e. Identify the decay mode and explain why the proton number changes.

3.An excited technetium nucleus changes as ⁹⁹ᵐ₄₃Tc → ⁹⁹₄₃Tc + γ. What type of decay is this, and what changes in the nucleus?

Balance the nuclear equations

Fill each gap by conserving both nucleon number and proton number. Give the nuclide symbol, including its element symbol where possible.

4.Complete the alpha-decay equation: ²¹⁰₈₄Po → + ⁴₂He.

5.Complete the beta-minus equation: ⁹⁰₃₈Sr → + ⁰₋₁e.

6.Complete the equation and name the emitted particle: ²³⁸₉₂U → ²³⁴₉₀Th + ____.

7.A daughter nucleus ¹³¹₅₄Xe is formed by beta-minus decay. Complete the parent nucleus: → ¹³¹₅₄Xe + ⁰₋₁e.

8.Complete the gamma-emission equation: ¹⁵²ᵐ₆₃Eu → ____ + γ. Explain why the daughter keeps the same A and Z.

Investigate a decay chain

A nucleus can decay more than once. Follow the changes carefully and use the first daughter as the parent of the next step.

9.Radon-222 undergoes alpha decay. Write the complete nuclear equation, including the daughter nuclide and emitted particle.

10.Tritium undergoes beta-minus decay: ³₁H → ____ + ⁰₋₁e. Find the daughter nuclide and verify conservation of A and Z.

11.A student says, “In beta-minus decay, the daughter has one extra nucleon.” Use ¹⁴₆C → ¹⁴₇N + ⁰₋₁e to assess the claim and correct it.

12.A mystery decay is written ²⁴₁₁Na → ²⁴₁₂Mg + ____. Determine the missing particle and the decay mode. Use changes in A and Z to justify your answer.