Atoms and nuclear radiation

• Some atoms are radioactive
• Types of ionising radiation

  • Alpha
  • Beta
  • Gamma
• Atom


  Made up of a nucleus with electrons orbiting around it
• Nucleus


  Contains two types of particle: protons and neutrons
• Unstable atoms are radioactive because they emit ionising radiation from their nuclei to become more stable
• Radioactive decay


  The process by which unstable atoms emit ionising radiation to become more stable
• There is no way of predicting when an unstable nucleus will emit radiation because it is a random event
• Radiation emitted from the nucleus is called nuclear radiation
• Three types of nuclear radiation

  • Alpha
  • Beta
  • Gamma
• You cannot tell that an atom is radioactive by looking at it
• Radioactivity was discovered by accident when a packet of uranium salts turned photographic film black
• Photographic film is used to check how much radiation people are exposed to
• People who work with radioactive materials wear film badges
• Geiger counter


  Detects radioactivity by clicking each time a particle of ionising radiation enters the Geiger tube
• A Geiger counter will always detect a low level of radiation, even if it is not near a source of radiation
• Background radiation


  Radiation that comes from space and from rocks and soil
• Carbon-14 is an example of an unstable atom
• Carbon-14 emits beta particles to become stable
• Beta is a type of ionising radiation
• A student suggests that their mobile phone is radioactive
• Count rate with phone switched off is 30 counts per minute
• Count rate with phone switched on is 28 counts per minute
• Count rate when the phone is not in the room is 29 counts per minute
• Measurements recorded by the Geiger counter can help determine if the phone is radioactive
• Nucleus


  The central part of an atom that contains the protons and neutrons.
• Alpha particles


  High-energy helium nuclei that can travel only a short distance through the air before being stopped.
• Beta particles


  High-energy electrons or positrons that can travel a few millimeters through the air.
• Gamma rays


  High-energy photons that can travel several meters through the air.
• Nuclear radiation


  Energy emitted from the nucleus of an atom, including alpha particles, beta particles, and gamma rays.