Radioactive Decay Types

Overview

• Three types of radioactive decay: alpha decay, beta decay, gamma decay
• Key concepts in nuclear physics, important for nuclear medicine

Alpha Decay

• Definition: Emission of an alpha particle (2 protons, 2 neutrons — equivalent to a helium nucleus)
• Effects on Atom:
  • Mass number decreases by 4
  • Atomic number decreases by 2
  • Transformation into a different element
• Properties:
  • Energetic but low penetration power
  • Stopped by paper or skin
  • Dangerous if ingested or inhaled (e.g. poisoning cases like Alexander Litvinenko)
• Health Impact:
  • Damages DNA, forms free radicals
  • Reduces white blood cell count, affects organs (liver, kidneys, spleen, bone marrow)
  • Symptoms include nausea, vomiting, hair loss
• Historical Cases:
  • Marie Curie’s daughter died from leukemia linked to polonium exposure

Beta Decay

• Definition: Emission of beta particles (high-energy electrons)
• Types:
  • Beta-plus decay: Proton turns to neutron, emits beta-plus particle and neutrino
  • Beta-minus decay: Neutron turns to proton, emits beta-minus particle and electron antineutrino
• Effects on Atom:
  • Beta-plus: Neutron gain, proton loss
  • Beta-minus: Proton gain, neutron loss
• Properties:
  • Smaller than alpha particles, can travel further
  • Stopped by clothing or aluminum foil
• Applications:
  • Brachytherapy: Used in cancer treatment
  • PET Scanning: Uses isotopes like Fluorine-18
• Special Notes:
  • Positrons emitted in beta-plus decay are similar to electrons but with positive charge

Gamma Decay

• Definition: Emission of gamma-ray photons (no particles ejected)
• Properties:
  • High-energy electromagnetic radiation
  • Penetrates most materials, absorbed by thick lead or concrete
• Effects on Atom:
  • No change in atomic structure or composition
  • Atom does not change to another element
• Applications:
  • Medicine: Gamma knife for cancer treatment
  • Food Preservation: Kills bacteria and sterilizes without significant changes to food

Summary

• Alpha Decay: Nucleus loses 2 protons; changes to a different element
• Beta Decay: Proton loss (beta-plus) or gain (beta-minus); changes to a different element
• Gamma Decay: No change in proton number; atom remains the same
• Health Impact:
  • Alpha: Least penetrating; dangerous if ingested
  • Gamma: Most penetrating; used in medical and industrial applications