Radioactivity

• The unit for radioactive decay is bequerels (Bq)
• Alpha particles are helium nuclei with two protons and two neutrons.
• Radioactive decay can occur by alpha, beta or gamma emission
• When an atom decays by emitting an alpha particle it loses four units of charge and becomes a different element.
• A beta minus particle is an electron that is emitted from the nucleus during nuclear decay.
• Gamma rays have the highest energy but lowest mass out of all three types of radiation.
• A half-life is the time taken for one half of the original number of atoms to undergo radioactive decay.
• Half life is measured in seconds, minutes, hours, days, years etc.
• Gamma rays have no charge and no rest mass.
• Gamma rays do not ionise atoms as they pass through them so cannot cause damage to living tissue.
• Alpha particles are stopped by paper, beta particles are stopped by aluminium foil and gamma rays are stopped by lead.
• Radiation detectors include Geiger counters and scintillation screens.