Radiation

• some elements are unstable. To become more stable, the nuclei of their atoms emit radiation
• by emitting radiation, the nucleus changes. This is a random process called radioactive decay
• to become more stable, a nucleus can:

  • emit some of its mass as nuclear radiation, or
  • decrease its internal energy by emitting high-frequency electromagnetic radiation
• each type of nuclear radiation emitted by unstable nuclei is ionising. This means that it can remove electrons from the outer orbits of other atoms, leaving them positively charged. If atoms in your cells are ionised, it can be very damaging to your body
• Alpha:

  • A nucleus of helium. Two protons and two neutrons.
  • +2 charge
  • relatively large mass
  • very strong ionising effect
• Beta:

  • an electron e-
  • -1 charge
  • very small mass
  • weak ionising effect
• gamma

  • an electromagnetic wave
  • 0 charge
  • no mass
  • very weak ionising effect
• neutron

  • a neutron particle inside the nucleus of an atom
  • 0 charge
  • large mass
  • very strong ionising effect
• both alpha and neutrons are heavy particles and have very high ionising power. As alpha are blocked by skin, they are most dangerous when the radioactive source is inside you. Neutrons are more dangerous when the source is outside your body, because neutrons have very high penetration power
• Gamma rays have no mass or charge, so do not interact with other particles as strongly as alpha particles. This means that gamma rays are not very ionising, but they are also not easily decelerated, so they are more penetrating than alpha particles. Neutrons are not typically able to ionise an atom directly because of their lack of charge, but they are indirectly ionising, as they are absorbed by stable nuclei. These nuclei will become more unstable by the absorption of a neutron, and more likely to emit ionising radiation of another type.
• Types of radiation

  A) alpha

  B) beta

  C) gamma

  
• neutrons can easily penetrate most materials. But they are slowed and blocked by materials that are rich in hydrogen. Thick concrete walls are good radiation shields because they can block both neutrons and gamma rays