AQA GCSE Combined Science: Physics: Atomic Structure and Radioactivity
6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Alpha, beta and gamma are three types of nuclear radiation emitted by unstable nuclei. They differ in what they are made of, how far they penetrate, and how strongly they are absorbed by different materials.
Compare alpha, beta and gamma radiation. In your answer you should refer to what each type is, its penetrating power (what stops it), and its relative ionising power. (6 marks)
A sample of a radioactive isotope is monitored with a detector. The count rate (corrected for background) is recorded over time, as shown below.
| Time / hours | Count rate / counts per second |
|---|---|
| 0 | 800 |
| 3 | 400 |
| 6 | 200 |
| 9 | 100 |
| 12 | 50 |
(a) Use the data to determine the half-life of this isotope. Explain how you obtained your answer. (2 marks)
(b) Predict the count rate you would expect at a time of 15 hours, assuming the same trend continues. (2 marks)
A radioactive source has an initial activity of 6400 Bq. Its half-life is 8 days.
(a) Calculate the activity of the source after 24 days. (2 marks)
(b) State the fraction of the original radioactive nuclei that remain undecayed after these 24 days. (1 mark)
In the early 20th century, the nuclear model of the atom replaced the earlier "plum pudding" model, largely because of the alpha-particle scattering experiment, in which alpha particles were fired at a very thin sheet of gold.
(a) State two observations from the alpha-scattering experiment. (2 marks)
(b) State one conclusion about the structure of the atom that these observations led to. (1 mark)
Radioactive contamination and irradiation are two different hazards when working with radioactive sources.
Explain the difference between radioactive contamination and irradiation. (2 marks)
Atoms of the same element can exist as different isotopes.
Define what is meant by isotopes of an element. (1 mark)