Radiation and isotopes

• Types of radiation


  • Alpha
  • Beta
  • Gamma
• Becquerel (Bq)


  Unit of radioactivity, amount of background radiation
• Sievert (Sv)


  Unit of radiation exposure dose to a person
• Radiation can mutate cells and cause cancer
• Ways to reduce radiation exposure

  • Keep as far away as possible
  • Spend as little time as possible near the site
  • Use shielding
• Alpha radiation always loses 2 protons and 2 neutrons from the atomic mass
• Beta radiation always loses 1 electron from the atomic mass
• Gamma radiation does not change the atomic mass
• Isotopes


  Different forms of the same element
• Isotopes


  • Have the same number of protons
  • Have a different number of neutrons
• Atomic number


  The number of protons in the nucleus of an atom
• Mass number


  The total number of protons and neutrons in the nucleus of an atom
• Isotopes of an element have the same number of protons but a different number of neutrons
• Isotopes can have different stabilities, but there are usually only one or two stable ones
• Radioactive decay


  1. Unstable nuclei try to become more stable by balancing the number of protons and neutrons

  2. Emit radiation to get rid of excess particles
• Alpha particles


  • Don't penetrate far into materials
  • Strongly ionizing
• Beta particles


  High-speed electrons emitted from the nucleus
• Beta particles


  • Moderately ionizing
  • Penetrate moderately far into materials
• For every beta particle emitted, a neutron in the nucleus has turned into a proton
• Gamma rays


  Electromagnetic waves with a short wavelength emitted from the nucleus
• Gamma rays


  • Penetrate far into materials without being stopped
  • Easily ionizing
• Gamma rays can be absorbed by thick sheets of lead or metres of concrete
• Uses of radiation


  • Sterilising medical equipment
• Alpha radiation would not be suitable for sterilising medical equipment as it is easily absorbed
• Nuclear equations


  Show radioactive decay using element symbols
• Mass and atomic numbers must balance on both sides of a nuclear equation
• Alpha decay


  Decreases the charge and mass of the nucleus by 2 and 4 respectively
• Beta decay


  Increases the charge of the nucleus by 1
• Gamma rays don't change the charge or mass of the nucleus
• Radioactive decay is a totally random process
• Activity


  The rate of radioactive decay, measured in becquerels (Bq)
• The radioactivity of a source decreases over time
• Half-life


  The time taken for the number of radioactive nuclei, the activity or the count-rate to halve
• Measuring half-life


  1. Plot a graph of activity against time

  2. The half-life is the time interval corresponding to half the initial activity
• Exposure to radiation is called irradiation
• Contamination is radioactive particles getting onto objects
• Risks of radiation


  • Irradiation can cause harm to the body
  • Contamination can lead to radioactive particles getting stuck to the skin or inside the body
• The seriousness of irradiation and contamination depends on the source of the radiation
• Alpha sources are the most dangerous as their radiation can't penetrate far but is highly ionizing
• Understanding how different types of radiation affect the body is important for safety