P4

• isotopes are different forms of the same element, the same number of protons different number of neutrons

  unstable isotopes decay and give out radiation to become stable - radioactive decay
• radioactivity can be measured by counting how many times it decays per second
• the half life of an unstable nucleus is the time taken for half its atoms to decay into another form
• alpha particles have two protons and two neutrons so they are helium nuclei
• alpha particles only travel few cm in the air, and don't penetrate and are very ionising
• beta particles - high speed electrons and have no mass 1/2 the mass of a proton, moderately ionising and do penetrate 1-2mm, they have a range in air of a few metres
• gamma rays are waves of electromagnetic radiation released by the nucleus, penetrate far into materials and travel long distance through the air, they are weakly ionising and absorbed ny lead

  gamma radiation takes place due to nucleus having excess energy
• radioactivity is the rate of decay in a sample of radioactive material

  half life is the time it takes for the activity to half

  overtime, activity decreases due to there being fewer unstable nuclei left

  background radiation = low level radiation

  irradiation - exposure to radiation