Nuclear radiation and radioactive decay: Physics AQA: GCSE (9:1)

• Stable nuclei


  Nuclei that contain a certain amount of neutrons compared to protons
• Unstable nuclei


  Nuclei with too few or too many neutrons
• Radioactive decay

  A random process in which an unstable nucleus will emit one or more types of nuclear radiation to become more stable

  
• Nuclear radiation

  Radiation emitted from an unstable nucleus during radioactive decay

  
• Types of nuclear radiation

  Alpha particle, beta particle, gamma ray, neutron
• Alpha particle (α)


  Consists of two neutrons and two protons and is identical to a helium nucleus

  
• Beta particle (β)


  A high speed electronejected from the nucleus

  
• Gamma ray (γ)


  Electromagnetic radiation from the nucleus

  
• Change to the nucleus due to alpha decay

  The nucleus loses two protons and two neutrons

  
• Effect of alpha decay on atomic and mass numbers

  The mass number decreases by four and the atomic number decreases by two

  
• Change to the nucleus due to beta decay

  A neutron turns into a proton

  
• Effect of beta decay on atomic and mass numbers

  The atomic number increases by one and the mass number remains the same

  
• Change to the nucleus due to gamma decay

  There is no change to the particles in the nucleus

  
• Effect of gamma decay on atomic and mass numbers

  There is no change to the atomic or mass numbers

  
• Geiger-Muller (GM) tube

  A device that can detect ionising radiation and is used to measure the activity of a radioactive source

  
• activity


  the rate at which a source of unstable nuclei decays
• becquerels (Bq)

  the SI unit for activity
• count-rate


  the number of decays recorded each second by a detector