MCQs – Radioactive decay (set 1)

The decay constant of a certain radionuclide is 1.07 × 10⁻⁴ yr⁻¹. What is its half-life?

• 8900 yr

• 7000 yr

• 6500 yr

• 5000 yr

In a radioactive decay series, three successive decays each result in a particle being emitted. The first decay results in the emission of a β-particle. The second decay results in the emission of an α-particle. The third decay results in the emission of another β-particle. Nuclides P and S are compared. Which statement is correct?

• P and S are identical in all respects.

• P and S are isotopes of the same element.

• S is a different element of lower atomic number.

• S is a different element of reduced mass.

Copper-66 decays to Zn, such that 7/8 of the copper atoms have decayed in 15 minutes. What is the half-life of copper-66?

• 15 min

• 10 min

• 7.5 min

• 5 min

In the following processes, J, K, L, M and N represent unknown emissions. Which process represents a γ-decay?

Radioactive decay is said to be a spontaneous process. This means that:

• we cannot know when a nucleus will decay.

• we cannot know which nucleus will decay next.

• we cannot know how many nuclei will decay.

• we cannot influence when a nucleus will decay.

Some rocks contain lead as a result of radioactive decay. In one such decay, a fixed amount of polonium decays to a stable isotope of lead.

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The grid shows a number of nuclides arranged according to the number of protons and the number of neutrons in each. A nucleus of the nuclide ⁸₃Li decays by emitting a β-particle. What is the resulting nuclide?

• A

• B

• C

• D

The half-life of astatine-215 is 100 μs. How much time does it take for the activity of a sample to decay to 6.25% of its initial value?

• 400 μs

• 6.25 μs

• 40 μs

• 300 μs

What is not conserved in nuclear processes?

• charge

• momentum

• the total number of neutrons

• the total number of nucleons

A radioactive nucleus is formed by β-decay. The nucleus then decays by α-emission. Which graph of proton number Z plotted against nucleon number A shows the β-decay followed by the α-emission?

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