Nuclear Reactions and Half-Life

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 (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 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

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 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

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

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