Radioactive Decay

• State four types of nuclear radiation.

  Alpha particles, Beta particles, Gamma rays, Neutron emission
• What is meant by background radiation?

  Radiation that is always present, in small amounts so not harmful
• Give 4 sources of background radiation.

  Rocks, cosmic rays from space, nuclear weapons testing, nuclear accidents.
• How do you measure and detect background radiation?

  Photographic film, Geiger-Muller counter.
• How is photographic film used to measure radiation?

  Turns dark when it absorbs radiation.
• How are Geiger-Muller tUbers used to measure radiation.

  Produces a pulse when it absorbs radiation, which is used to count the amount of radiation. The frequency demonstrates the amount of radiation.
• What constitutes an alpha particle?

  Two protons and two neutrons, it is the same as a helium nucleus.
• What is the range of an alpha particle through air?

  A few centimetres (normally 2-10cm range)
• What will block beta radiation?

  A few mm of aluminium or several metres of air.
• What will block gamma radiation?

  Several cm of lead, a few metres of concrete.
• Describe the plum pudding model of the atom.

  A sphere of positive charge, with the negatively charged electrons distributed evenly throughout it.
• Which experiment disproved the plum-pudding model?

  Rutherford‘s alpha-Scattering/gold-foil experiment.
• What is the currently accepted model of atom called?

  The Bohr model.
• Describe Rutherford‘s experiment.

  Alpha particles (+2 charge) fired at a thin sheet of gold foil, most went straight through but some were deflected by acute angles and some by larger ones.
• What did Rutherford‘s experiment prove?

  Most of the atom is empty space, the nucleus has a positive charge, most of the mass is concentrated in the nucleus.
• What happens during beta+ decay?

  A proton turns into a neutron and a positron to conserve charge.
• What occurs when a neutron changes into a proton and an electron?

  Beta- decay.
• What does alpha decay do to the atom?

  The atomic number decreases by 2 and the mass number decreases by 4, a new element is formed.
• What does beta- decay do to the atom?

  The mass number stays the same, the atomic number increases by 1, a new element is formed.