Radioactive Decay Practice Questions

Which of these describes an alpha particle?

☐ A an electron emitted from the nucleus

☐ B a nucleus of helium, containing two protons and two neutrons

☐ C a high-frequency electromagnetic wave

☐ D a positron emitted from the nucleus

Put a cross ( ☒ ) in the box next to your answer.

State the unit of the activity of a radioactive source.

Other than alpha, name two other types of ionising radiation that can be emitted from an unstable nucleus.

Explain what is meant by background radiation.

Describe one origin of background radiation that comes from the Earth and one that comes from space.

Explain what is meant by the half-life of a radioactive isotope.

Calculate the activity of this sample after 24 days.

activity = .............................................................. Bq

Calculate the count rate from the source alone, with no absorber in place.

count rate = .............................................................. counts per minute

Deduce which types of radiation this source emits. Use the data in the table in your answer.

Radium-226 decays by alpha emission to radon-222.

Complete the nuclear equation for this decay.

$$^{226}_{88}\mathrm{Ra} \rightarrow\ ^{222}_{86}\mathrm{Rn} + {}^{\square}_{\square}\alpha$$

A nucleus of beryllium-13 decays by emitting a neutron.

State the effect of this emission on the mass number and on the atomic number of the nucleus.

The diagram represents a nucleus before and after it emits radiation.

Which type of decay is represented in the diagram?

☐ A alpha

☐ B beta minus

☐ C beta plus

☐ D neutron emission

Put a cross ( ☒ ) in the box next to your answer.

Describe the process of beta plus decay inside the nucleus.

Complete the nuclear equation for the decay of fluorine-18.

$$^{18}_{9}\mathrm{F} \rightarrow {}^{\square}_{\square}\mathrm{O} + {}^{0}_{+1}\beta$$

Determine the half-life of this isotope. Use data from the table in your answer.

Calculate the activity of this sample 60 hours after the first measurement.

activity = .............................................................. Bq

Calculate the mean count rate from the granite, corrected for background radiation.

mean count rate = .............................................................. counts per minute

The student says the five readings should all have been the same, and that the experiment must have been done carelessly.

Explain why readings like these are expected in a radioactivity experiment.

Describe how a teacher could use a GM tube and counter to investigate how the count rate from this gamma source changes with the distance between the source and the tube.

Photographic film can also be used to detect radiation. Describe how.

Explain how alpha, beta and gamma radiations differ in their penetrating power and ionising power, and describe how the teacher could use the equipment to find out which types of radiation this source emits.

Calculate the number of undecayed nuclei remaining in the sample after 2 hours.

number of undecayed nuclei = ..............................................................

State the net decline in the number of undecayed nuclei over these 2 hours, as a ratio.

Calculate the half-life of this isotope.

half-life = .............................................................. hours

Explain why it is impossible to predict when one particular nucleus in this sample will decay, even though the activity of the whole sample 20 hours later can be predicted confidently.