Radioactive decay

• What are the four types of nuclear radiation?

  Alpha particles, beta particles, gamma rays, and neutrons
• What is meant by background radiation?

  Radiation that is always present in very small amounts and is not harmful
• Name four sources of background radiation.

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

  Using photographic film and a Geiger-Muller counter
• How is photographic film used to measure radiation?

  A photographic film turns dark when it absorbs radiation, indicating exposure levels
• How are Geiger-Muller tubes used to measure radiation?

  They produce a pulse when absorbing radiation, which is counted to determine radiation levels
• What constitutes an alpha particle?

  Two protons and two neutrons, equivalent to a helium nucleus
• What is the range of an alpha particle through air?

  A few centimeters, typically in the range of 2-10 cm
• What will block beta radiation?

  A thin sheet of aluminium or several meters of air
• What will block gamma radiation?

  Several centimeters of lead or a few meters of concrete
• Which type of radiation is most ionising?

  Alpha radiation
• Which type of radiation is least ionising?

  Gamma radiation
• How does gamma emission affect the mass and charge of an atom?

  Both mass and charge remain unchanged
• Describe the plum-pudding model of the atom.

  A sphere of positive charge with negatively charged electrons distributed evenly throughout it
• What was believed about the atom prior to the discovery of the electron?

  The atom was believed to be indivisible
• Which experiment led to the plum-pudding model being discarded?

  Rutherford’s alpha-scattering experiment
• What is the name given to the currently accepted model of the atom?

  The Bohr model
• Describe Rutherford’s experiment.

  Alpha particles were fired at a thin sheet of gold foil, with most passing through and some being deflected
• What are the conclusions of Rutherford’s experiment?

  Most of an atom is empty space, the nucleus has a positive charge, and most of the mass is concentrated in the nucleus
• What happens in the process of beta plus decay?

  A proton turns into a neutron and a positron to conserve charge
• What is the process called when a neutron changes into a proton and an electron?

  Beta minus decay
• When alpha decay occurs, what happens to the atomic number and mass number of the atom?

  The atomic number decreases by 2, the mass number decreases by 4, and a new element is formed
• What effect does beta minus decay have on the mass number and atomic number of an atom?

  The mass number stays the same, and the atomic number increases by 1