Isotopes and nuclear radiation

• Isotopes


  Different forms of the same element
• Isotopes


  • Have the same number of protons (same atomic number)
  • Have a different number of neutrons (different mass number)
• Elements have different isotopes, but there are usually only one or two stable ones</b>
• Radioactive decay


  Unstable isotopes try to become more stable by balancing the number of protons and neutrons in the nucleus or getting rid of excess energy
• Radioactive substances


  Emit alpha, beta and gamma radiation
• Radioactive substances


  Can also release neutrons when they decay
• Ionising radiation


  Radiation that knocks electrons off atoms, creating positive ions
• Ionising power


  How easily a radiation source can ionise atoms
• Alpha particles


  • Helium nuclei
  • Strongly ionising
  • Can only travel a few cm in air
  • Absorbed by a sheet of paper
• Beta particles


  • High-speed electrons
  • Moderately ionising
  • Can travel a few metres in air
  • Absorbed by a sheet of aluminium
• For every beta particle emitted, a neutron in the nucleus has turned into a proton
• Gamma rays


  • Electromagnetic radiation
  • Weakly ionising
  • Penetrate far into materials
  • Absorbed by thick sheets of lead or metres of concrete