Nuclear Reactions and Half-Life

Nuclear Reactions

• A nuclear reaction is a process in which atomic nuclei interact, resulting in a change to the nucleus
• Types of nuclear reactions:
  • Nuclear fission: a heavy nucleus splits into two or more lighter nuclei
  • Nuclear fusion: two or more light nuclei combine to form a heavier nucleus
  • Radioactive decay: a nucleus emits radiation to become more stable

Half-life

• Half-life (t1/2) is the time it takes for half of the radioactive atoms in a sample to decay
• Half-life is a constant for a given radioactive substance
• Half-life can range from fractions of a second to billions of years
• After one half-life, half of the original sample remains
• After two half-lives, one-quarter of the original sample remains
• After three half-lives, one-eighth of the original sample remains, and so on

Radioactive Decay

• Radioactive decay is a random process in which unstable nuclei release energy and particles to become more stable
• Decay modes:
  • Alpha decay: emission of an alpha particle (2 protons and 2 neutrons)
  • Beta decay: emission of a beta particle (electron or positron)
  • Gamma decay: emission of gamma radiation (high-energy photons)
• Radioactive decay is a first-order process, meaning the rate of decay is proportional to the number of radioactive atoms present

Types Of Radiation

• Ionizing radiation: radiation with enough energy to remove tightly bound electrons from atoms, resulting in ionization
  • Alpha particles
  • Beta particles
  • Gamma rays
  • X-rays
• Non-ionizing radiation: radiation without enough energy to remove tightly bound electrons from atoms
  • Radio waves
  • Microwaves
  • Infrared light
  • Visible light

Ionizing Radiation

• Ionizing radiation can cause harm to living organisms by damaging DNA and other biological molecules
• Effects of ionizing radiation:
  • Genetic mutations
  • Cancer
  • Radiation sickness
  • Cell death
• Units of ionizing radiation:
  • Becquerel (Bq): one disintegration per second
  • Gray (Gy): absorbed dose of ionizing radiation
  • Sievert (Sv): biological effect of ionizing radiation

Nuclear Reactions

• Atomic nuclei interact, resulting in a change to the nucleus
• Nuclear fission: heavy nucleus splits into two or more lighter nuclei
• Nuclear fusion: two or more light nuclei combine to form a heavier nucleus
• Radioactive decay: nucleus emits radiation to become more stable

Half-life

• Time it takes for half of the radioactive atoms in a sample to decay
• Constant for a given radioactive substance
• Ranges from fractions of a second to billions of years
• After one half-life, half of the original sample remains
• After two half-lives, one-quarter of the original sample remains
• After three half-lives, one-eighth of the original sample remains, and so on

Radioactive Decay

• Random process: unstable nuclei release energy and particles to become more stable
• Decay modes: alpha, beta, and gamma decay
• Alpha decay: emission of an alpha particle (2 protons and 2 neutrons)
• Beta decay: emission of a beta particle (electron or positron)
• Gamma decay: emission of gamma radiation (high-energy photons)
• First-order process: rate of decay is proportional to the number of radioactive atoms present

Types Of Radiation

• Ionizing radiation: enough energy to remove tightly bound electrons from atoms, resulting in ionization
• Alpha particles, beta particles, gamma rays, and X-rays are ionizing radiation
• Non-ionizing radiation: without enough energy to remove tightly bound electrons from atoms
• Radio waves, microwaves, infrared light, and visible light are non-ionizing radiation

Ionizing Radiation

• Causes harm to living organisms by damaging DNA and other biological molecules
• Effects: genetic mutations, cancer, radiation sickness, and cell death
• Units of ionizing radiation: Becquerel (Bq), Gray (Gy), and Sievert (Sv)
• Becquerel (Bq): one disintegration per second
• Gray (Gy): absorbed dose of ionizing radiation
• Sievert (Sv): biological effect of ionizing radiation