C7

• Relative atomic

  mass

  Number of protons

  and neutrons
• Atomic number


  Number of protons
• Atom


  The smallest possible piece of an element. Has

  a radius of 0.1nm
• Element


  A substance in which all the atoms have the

  same atomic number.
• Isotope


  Atoms with the same number of protons but

  different numbers of neutrons.
• Nucleus


  The centre of an atom. Contains protons and

  neutrons
• Proton


  A positively charged particle found in the

  nucleus
• Neutron


  A neutral particle found in the nucleus.
• Electron


  A negatively charged particle found in energy

  levels (shells) around the nucleus
• Radioactivity


  Substances with unstable nuclei that emit ionising

  radiation to become stable
• Becquerel, Bq


  The unit of radioactive decay.

  1 becqurel = 1 nucleus decaying per second
• Geiger-Muller tube


  A device to measure the count rate of a

  radioactive source
• Count rate


  The number of decays recorded per second

  by a detector
• Ionisation


  When atoms becomes charged because

  they lose / gain electrons
• Half-life


  The time it takes for the number of radioactive

  nuclei in a sample to halve
• Radioactive

  contamination


  Unwanted presence of materials containing radioactive

  atoms on other materials
• Irradiation


  When something is exposed to ionising radiation,

  but does not become radioactive itself
• Background radiation


  Low levels of ionising radiation from natural and

  man-made sources around us
• Sievert, Sv


  The unit of ionising radiation dose
• what is the LEAST penetrating out of alpha, beta, gamma

  alpha
• which is the MOST harmful out of alpha, beta, gamma

  gamma