Definitions - radioactivity

• Atomic number


  The number of protons in the nucleus of an atom which is characteristic of a chemical element and determines its place in the periodic table
• Contamination


  Occurs when material that contains radioactive atoms is deposited on materials, skins, clothing, or any place where it is not desired
• Electron


  A (subatomic) particle with a negative charge that orbits the nucleus of an atom
• Half life


  The time taken for the radioactivity of a specified isotope to fall to half its original value
• Ionisation


  The process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions
• Irradiation


  The process by which an object is exposed to radiation
• Isotope 


  Different atoms of a chemical element in a periodic table all have the same number of protons but may have a different number of neutrons in their nuclei
• Geiger-Muller tube


  An instrument or detecting ionising radiation
• Mass number


  The total number of protons and neutrons in a nucleus
• Neutron


  A (subatomic) particle with no charge (neutral) that is found in the nucleus of an atom
• Nucleus 


  The positively charged central core of an atom, consisting of protons and neutrons
• Proton


  A (subatomic) particle with a positive charge that is found in the nucleus of an atom
• Radiation 


  The emission of energy in the form of waves or particles from the nucleus of an atom