Atoms and Nuclear Radiation

• Why do unstable nuclei emit radiation?

  To become more stable through decay
• What is the process called when an unstable nucleus emits radiation?

  Radioactive decay
• How is the activity of an unstable nucleus defined?

  As the rate of decay of unstable nuclei
• What is the unit of radioactive activity?

  Becquerel (Bq)
• What does count-rate refer to in radioactivity?

  The number of decays per second
• Name a detector used to measure count-rate.

  Geiger-Muller tube
• What are the four types of nuclear radiation?

  • Alpha particles
  • Beta particles
  • Gamma rays
  • Neutrons
• What are the constituents of an alpha particle?

  Two protons and two neutrons
• What is the range of an alpha particle in air?

  A few centimetres (2-10 cm)
• What can stop beta radiation from passing through?

  A thin sheet of aluminium
• What will stop gamma radiation from passing through?

  Several centimetres of lead
• Which type of radiation is most ionising?

  Alpha radiation
• Which type of radiation is least ionising?

  Gamma radiation
• What changes occur to mass or charge during gamma ray emission?

  Both mass and charge remain unchanged
• Describe the nature of radioactive decay.

  • Random process
  • Decay determined by chance
  • Impossible to predict specific decays
• What is the half-life of a radioactive isotope?

  The time for unstable nuclei to halve
• What is radioactive contamination?

  Unwanted radioactive nuclei on materials
• What is irradiation?

  Exposing a material to nuclear radiation
• Why is it important to publish radiation study results?

  • Allows independent checking of findings
  • Known as peer review