Radioactivity

• Radioactivity


  The spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation
• Alpha particles


  Groups of two protons and two neutrons stuck together, the same as the nucleus of the helium atom
• Alpha particles


  • Carry a double positive charge
  • Travel relatively slowly compared to other types of radiation
  • Have a low penetrating power and are stopped by a few centimetres of air or a sheet of paper
• Beta particles


  Fast-moving electrons
• Beta particles


  • Can be inhaled or ingested and can be very harmful to internal organs such as the lungs, liver and kidneys, and can give rise to cancers
• Gamma radiation


  High energy electromagnetic radiation, similar to X-rays, that travels at the speed of light
• Gamma radiation


  • Has a very high penetrating ability and can penetrate bricks and metal sheets
  • Is the most dangerous of the three types of radiation as it can change the structure of the chemicals in our bodies and give rise to cancer
• An example of a radioactive element that emits alpha particles is americium-241, which is commonly used in smoke detectors
• An example of an element that emits beta particles is carbon-14, which is used in carbon dating
• An example of an element that gives off gamma rays is cobalt-60, which is often used in hospitals in the treatment of cancer patients
• In a chemical reaction, bonds are broken and new bonds are formed, but the nuclei of the atoms stay the same
• In a nuclear reaction, the composition, structure or energy of an atomic nucleus is altered, resulting in the formation of a new element
• When an atom loses an alpha particle, it changes into an atom of the element two places before it in the Periodic Table, and the mass number decreases by four
• When an atom loses a beta particle, the next nucleus has one extra proton and one neutron less, so the atomic number increases by one but the mass number stays the same
• Half-life


  The time taken for half the radioactive atoms in a sample to decay
• (An electron cannot have a mass number or an atomic number. The values of 0 and -1 are given to the electron simply to balance the equation.)
• The carbon atom changes into a nitrogen atom with the same mass number. The mass number stays the same since the extra proton in the new nucleus is balanced out by the loss of the neutron.
• As a double check that you have written a nuclear equation correctly, add up the atomic numbers of the products (7-1) and also the mass numbers of the products (14 + 0) and these should be equal to those in the parent atom (6 and 14 respectively).
• The loss of a beta particle


  An element may be changed into another element one place after it in the Periodic Table. The mass number of the parent atom stays the same.
• The loss of gamma radiation does not give rise to any new atoms-energy is simply lost from the nucleus.
• In the emission of alpha and beta particles from unstable nuclei, one element may be changed into another for most of the common elements around us, it is very difficult to change one element into another.
• Transmutation


  The changing of one element into another, which only occurs in nuclear reactions.
• Chemical reactions cannot change one element into a different element since chemical reactions merely involve electron changes-usually in the outer energy level.
• Half-life


  The time taken for half of the nuclei in any given sample to decay.
• Radioisotopes


  Isotopes of elements that are radioactive.
• Uses of radioisotopes

  • Medical uses
  • Archaeological uses
  • Agricultural research
  • Food irradiation
  • Smoke alarms
  • Industrial uses
• Most of the natural radiation in our environment comes from radioactive materials such as uranium and thorium found in rocks in the Earth.
• Radioactivity is also spread throughout the world as a result of nuclear weapons tests, accidents at nuclear power plants, and discharges from nuclear fuel processing plants.
• Many people are exposed to radiation because of the jobs they do, e.g. those who use radioactive isotopes in medicine and those working in the nuclear power industry.
• Great care should always be taken when working with radioactive sources. They should never be handled directly and gamma sources must always be stored in a lead container.