Atoms and nuclear radiation

• Why do unstable nuclei give out radiation

  • Unstable nuclei undergo decay to become more stable
  • as they release radiation their stability increases
• What is the name of the process in which an unstable nucleus gives out radiation to become stable 


  Radioactive decay
• define the activity of an unstable nucleus

  Activity is the rate of decay of a source of unstable nuclei
• What’s the unit of radioactive decay

  Becquerel (Bq)
• What is count rate

  The number of radioactive decays per second for a radioactive source
• Give an example of a detector that may be used to measure count rate

  Geiger-Muller tube
• State the four types of nuclear radiation

  1. Alpha particles
  2. beta particles
  3. gamma rays
  4. neutrons
• What are the constituents of an alpha particle

  • Two protons and two neutrons
  • it’s the same as a helium nucleus
• What’s the range of alpha particles through air

  A few centimetres typically 2-10
• What will stop beta radiation

  • A thin sheet of aluminium
  • several meters of air
• What will stop gamma radiation

  • Several centimetres of lead
  • a few meters of concrete
• What type of radiation is the most ionising

  Alpha
• What type of radiation is the least ionising

  gamma
• State any changes to mass or charge that occur due to the emission of a gamma ray

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

  • Random
  • which nuclei decays and when is determined only by chance
  • it is impossible to predict which nuclei will decay and when
• Define the half life of a radioactive isotope

  • The time it takes for the number of unstable nuclei in a substance to halve
  • the time it takes for the count rate from a sample to fall to half its initial level
• What is radioactive contamination

  The presence of unwanted radioactive nuclei on other materials
• What is irradiation

  • The process of exposing a material to nuclear radiation
  • the material does not become radioactive
• Why is it important for the results of studies on the effects of radiation to be published and shared with other scientists

  • To allow the findings to be independently checked
  • this is known as peer review