• Radioactivity involves the spontaneous emission of material and/or energy from the nucleus of an atom.
  • The most common radioactive atoms have high atomic numbers and contain a large excess of neutrons.
  • Some typical radioactive elements are technetium (atomic number 43), promethium ( atomic number 61), and all elements atomic number 84 (polonium) and higher.
  • Some elements considered to be stable do have radioactive isotopes.
  • Carbon-14 is radioactive, but this is only a small fraction of the total amount of carbon in existence.
  • Hydrogen also has a radioactive isotope known as hydrogen-3 or tritium.
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