types of radiation

• all atoms contain a nucleus which contain a different combination of protons and neutrons. the number of protons and neutrons can be calculated from the atom's symbol.

  the number of protons in a nucleus determines which element it is, e.g. if there are 6 protons in a nucleus it must be carbon, if there are 8 it is oxygen.

  
• isotopes:

  these nuclei are both carbon because they both have the same proton number, 6, but because their nucleon number is different, they have a different number of neutrons. they are known as isotopes.

  
• radioactive decay:

  • of the two isotopes of carbon (in the flashcard 'isotopes'), only carbon-12 is stable. carbon-14 is unstable because of an imbalance between the number of protons and neutrons in its nucleus. this means it will try to become more stable by releasing some radiation. this is called decaying.
  • this us a random process as it is impossible to guess when a nucleus will decay but estimations can be made from probability. this is similar to throwing several dice, you cannot guess which will land on 6 each time but you would expect roughly one sixth to land on 6.
  • due to its random nature, any measurements of radiation should be taken over a long time or repeated several times to reduce the effect of random fluctuations.
• background radiation:

  when measuring radiation, you must remember to adjust for background radiation. this low level of radiation is all around at all times. it is due to both natural and man-made sources.

  the level of background radiation varies from one place to another. this is due to the different rocks in each area, the types of buildings and height above sea level will affect how much radiation is emitted from cosmic rays.

  
• penetrating power:

  an investigation into a radioactive source such as the example below can be used to find the type of radiation emitted.

  
• in this example (penetrating power), there would be:

  330 cpm (counts per minute) of alpha as this was blocked by the thin card, no beta as aluminium did not block any extra cpm, 20 cpm of gama as 20cpm could penetrate the aluminium.

  
• there are three types of radiation produced from radioactive decay; alpha, beta and gamma.

  
• equations:

  there are two key things to remember when using an equation to represent nuclear decay.

  1. the total nucleon number must be the same before and after the reaction.
  2. the total proton number must be the same before and after the reaction.