Half-life: past paper questions

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• Question 37Oct/Nov 2024, paper 11Multiple choice1 mark

  The half-life of the radioactive isotope caesium ${}_{55}^{137}\text{Cs}$ is 30 years. Starting with 30 g of the isotope, which mass of the isotope remains after 90 years?

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• Question 36Oct/Nov 2023, paper 11Multiple choice1 markHas a diagram

  The graph shows the count rate from a radioactive source over a period of time. What is the half-life of the source?

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• Question 37May/June 2026, paper 23Multiple choice1 markHas a diagram

  Oxygen-15 is used in hospitals. The count rate from a detector placed close to a sample of oxygen-15 was recorded over a period of $15\text{min}$. The background count rate is $20\text{counts/min}$.

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• Question 37Oct/Nov 2025, paper 12Multiple choice1 mark

  An isotope of strontium decays by $\beta$ emission. It takes 87 hours for its activity to fall to $\frac{1}{8}$ of its original value. What is the half-life of the isotope?

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• Question 9May/June 2026, paper 32Structured7 marks

  Table 9.1 shows some features of three types of radioactive emission. The table is incomplete. Complete Table 9.1 by adding the missing information.

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• Question 36Oct/Nov 2024, paper 13Multiple choice1 markHas a diagram

  Half-life is ......1...... for the ......2...... a sample of a radioactive isotope to halve.

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• Question 35Oct/Nov 2023, paper 13Multiple choice1 markHas a diagram

  The half-life of carbon-14 is $5700\text{ years}$. An object containing carbon-14 has a count rate of $100\text{ counts / minute}$ when it is first formed. The graph shows how the count rate decreases over time.

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• Question 9May/June 2026, paper 33Structured7 marks

  Table 9.1 shows some features of three types of radioactive emission. The table is incomplete.

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• Question 36Oct/Nov 2025, paper 21Multiple choice1 markHas a diagram

  Which properties must a radioisotope have for its radiation to make it suitable to kill bacteria in food?

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• Question 37Oct/Nov 2024, paper 21Multiple choice1 mark

  An explosion in a nuclear reactor spreads the isotope caesium-137, ${}_{55}^{137}\text{Cs}$, across a large area. After 90.0 years have passed, the quantity of caesium-137 present is 12.5% of its original level. What is the half-life of caesium-137?

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• Question 36Oct/Nov 2023, paper 21Multiple choice1 markHas a diagram

  Radioisotope X decays to the stable isotope Y. The graph shows how the mass of Y present in a sample varies with time. Which time interval gives the half-life of X?

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• Question 9May/June 2026, paper 42Structured6 marksHas a diagram

  Carbon-14 is the only radioactive isotope of carbon that occurs naturally. State one similarity and one difference in the composition of the nuclei of atoms of different isotopes of the same element.

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• Question 10Oct/Nov 2025, paper 31Structured6 marks

  Radium is a radioactive element with the chemical symbol Ra. The proton number for radium is 88. Radium-223 is an isotope of radium that has a nucleon number of 223.

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• Question 37Oct/Nov 2024, paper 22Multiple choice1 mark

  The count rate measured near a radioactive source drops from $542\text{ counts per minute}$ to $94\text{ counts per minute}$ in 12 hours. The background count remains constant at $30\text{ counts per minute}$. What is the half-life of the source?

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• Question 10May/June 2026, paper 43Structured7 marks

  Carbon-14 and carbon-11 are different isotopes of carbon used in medicine. State the similarity and the difference between the composition of the nuclei of carbon-14 and carbon-11.

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• Question 9Oct/Nov 2025, paper 42Structured9 marksHas a diagram

  Fig. 9.1 shows a beam of radiation in a vacuum. The beam contains $\alpha$-particles, $\beta$-particles and $\gamma$-radiation. The beam enters a region where there is a strong, uniform magnetic field.

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• Question 36Oct/Nov 2024, paper 23Multiple choice1 mark

  Which definition of half-life is not correct?

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• Question 8Oct/Nov 2025, paper 43Structured7 marksHas a diagram

  Alpha ($\alpha$) particles are directed at a very thin sheet of gold foil. The following observations provide evidence for the nuclear model of the atom. State what conclusions may be made about the model of the atom from these observations.

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• Question 10Oct/Nov 2024, paper 32Structured8 marks

  Name three types of nuclear emission from radioactive sources.

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• Question 10Oct/Nov 2023, paper 31Structured5 marksHas a diagram

  A nucleus of an isotope of actinium contains 89 protons and 136 neutrons. The chemical symbol for actinium is Ac. Complete the nuclide notation for this isotope of actinium.

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• Question 10Oct/Nov 2024, paper 33Structured7 marks

  State how a neutral atom becomes a positive ion.

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• Question 11Oct/Nov 2023, paper 32Structured6 marksHas a diagram

  Fig. 11.1 represents all the particles in a beryllium atom. The symbol for the element beryllium is Be. Give the nuclide notation for the isotope shown in Fig. 11.1.

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• Question 8Oct/Nov 2024, paper 41Structured10 marksHas a diagram

  The nuclide notation for the radioactive isotope carbon-14 is ${}_6^{14}\mathrm{C}$. Using the symbols shown in Fig. 8.1, draw a diagram to show the number of electrons, neutrons and protons in a neutral atom of carbon-14 and how they are arranged.

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• Question 10Oct/Nov 2023, paper 33Structured5 marksHas a diagram

  Fig. 10.1 represents all the particles in a lithium atom. State the proton number (atomic number) of the lithium atom in Fig. 10.1.

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• Question 37May/June 2025, paper 23Multiple choice1 markHas a diagram

  An experiment is done to measure the radiation from a radioactive source. The source has a half-life of 10 minutes. The source is placed close to a detector that is connected to a counter, as shown.

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• Question 9Oct/Nov 2023, paper 43Structured10 marks

  For each application of radioactive isotopes, state and explain which type of radioactive emission is suitable and suggest an appropriate half-life for the isotope.

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• Question 10May/June 2025, paper 31Structured6 marks

  Table 10.1 describes four nuclides. Determine which two nuclides have the same number of nucleons.

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• Question 36May/June 2024, paper 21Multiple choice1 mark

  The reading on a detector placed near a radioactive material is 536 counts per second. The background count rate is 44 counts per second. The half-life of the radioactive material is 34 hours.

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• Question 37May/June 2023, paper 11Multiple choice1 markHas a diagram

  The count rate due to a sample of a radioactive isotope is measured for $80\text{ minutes}$.

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• Question 10May/June 2025, paper 32Structured7 marks

  Radon-222 is a radioactive gas that emits alpha ($\alpha$) particles. The nuclide notation for radon-222 is ${}_{86}^{222}\text{Rn}$. State the number of protons in one nucleus of radon-222.

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