P4 - Atomic Structure

• Atom


  Consists of a positively charged nucleus made up of protons and neutrons, surrounded by negatively charged electrons
• Nucleus


  The positively charged, dense region at the centre of an atom, made up of protons and neutrons, orbited by electrons
• Proton


  A particle with charge +1 found in the nucleus of an atom
• Neutron


  A neutral subatomic particle; a type of nuclear radiation, which can be emitted during radioactive decay
• Electron


  A particle with charge -1 that orbits an atom's nucleus
• Ion


  Formed when an atom loses or gains one or more electrons to become charged
• Element


  A substance that consists only of atoms with the same number of protons in their nuclei
• Atomic number


  The number of protons in an atom of an element
• Isotopes


  Atoms of the same element, but with different numbers of neutrons in the nucleus
• Unstable


  Lacking stability; having a very short lifetime; radioactive
• Activity

  The rate (in becquerels) at which a radioactive source emits radiation
• Radioactive


  Containing a substance that gives out radiation
• Alpha


  A type of radiation that is strongly ionising; a particle consisting of two neutrons and two protons (a helium nucleus)
• Beta


  A type of nuclear radiation that is moderately ionising; a high-speed electron, which is ejected from a nucleus as a neutron turns into a proton
• Gamma


  High frequency, short wavelength electromagnetic waves; a type of nuclear radiation, emitted from a nucleus
• Contamination


  The unwanted presence of materials containing radioactive atoms on other materials
• Irradiation


  To expose an object to nuclear radiation (the object does not become radioactive)
• Half-life


  The average time it takes for half the nuclei in a sample of radioactive isotope to decay; the time it takes for the activity of a radioactive isotope to fall by 50% (halve)
• Radiation:

  •Alpha - 2 neutrons, 2 protons

  •Beta - 1 electron

  •Gamma - electromagnetic waves
• Alpha:

  • Weakly penetrative

  • Strongly ionising
• Beta:

  •Moderately penetrative

  •Moderately ionising
• Gamma:

  •Strongly penetrative

  •Weakly ionising
• Alpha decay decreases charge and mass of a nucleus to make it unstable
• Beta decay increases the charge of a nucleus to make it unstable