Atomic Structure

• The half-life is the average time taken for the number of radioactive nuclei to halve
• The relative mass of an electron is 1 / 2000
• Electrons can move to higher energy levels if they gain energy. They might gain energy by absorbing light or other em radiation
• Electrons can fall to lower energy levels if they lose energy. This can be given off as em radiation
• The radius of an atom is approximately 1 x 10 ^ -10 m
• Alpha radiation / particle

  structure: 2 protons , 2 neutrons

  relative charge: 2 +

  relative mass: 4

  ionising power: high
• beta radiation / particle

  structure: a fast moving electron

  relative charge: 1 -

  relative mass: negligible

  ionising power: medium
• gamma radiation / particle

  structure: high frequency electromagnetic wave

  relative charge: 0

  relative mass: 0

  ionising power: low
• Penetration of the 3 radioactive decays:

  alpha: stopped by paper

  beta: stopped by a few mm of aluminium

  gamma: stopped by thick lead
• The random nature of radioactive decay is the where you can't predict which nucleus will decay next
• What is meant by the ‘random nature of radioactive decay’?

  Where you can't predict which nucleus will decay next
• nuclear weapons is an example of a man - made source of background radiation
• Explain how the process of nuclear fusion leads to the release of energy:

  • lighter nuclei join to form heavier nuclei
  • Some of the mass of the nuclei is converted to energy
• Explain the advantage of the radioactive waste having a shorter half-life:

  • the waste will decay at a greater rate
  • so the risk of harm decreases quickly
• Explain why contamination of the inside of the human body by a radioactive material that emits alpha radiation is highly dangerous:

  • alpha radiation is highly ionising
  • causing increased risk of cancer/ organ failure / radiation poisoning
  • until the radioactive material is excreted / removed
• Explain the ideal properties of a radioactive source for use in medical diagnosis.

  • short half-life so less damage to cells / tissues / organs / body

  • low ionising power so less damage to cells / tissues / organs / body

  • highly penetrating so it can be detected outside the body

  • emits gamma radiation