Overview
This lecture explains the four types of nuclear radiation—alpha, beta, gamma, and neutron—focusing on their properties, ionizing ability, and how easily they penetrate materials.
Isotopes and Radioactivity
- Elements exist as different isotopes with the same number of protons but varying numbers of neutrons.
- Most elements have only one or two stable isotopes; the rest are unstable and undergo radioactive decay.
- A material is called radioactive if it contains unstable isotopes that can decay.
Alpha Radiation
- Alpha particles consist of two protons and two neutrons, identical to a helium nucleus.
- Represented by helium's nuclear symbol (He).
- They have a +2 charge due to the absence of electrons.
- Alpha particles are large, strongly ionizing, but have low penetration—stopped by paper or a few centimeters of air.
Beta Radiation
- Beta particles are electrons with a -1 charge and almost no mass.
- Produced when a neutron in the nucleus decays into a proton (stays) and an electron (emitted).
- Beta particles are moderately ionizing and moderately penetrating—stopped by several meters of air or 5mm of aluminum.
Gamma Radiation
- Gamma rays are waves of electromagnetic radiation with no mass or charge.
- Often emitted after alpha or beta decay to release excess energy from the nucleus.
- Weakly ionizing but highly penetrating—require thick lead or meters of concrete to be stopped.
Neutron Emission
- Neutrons may be emitted if a nucleus has too many neutrons, increasing stability.
- Not much additional detail provided.
Recap of Radiation Types
- Alpha: two protons, two neutrons, stopped by paper.
- Beta: high-speed electron, stopped by thin aluminum.
- Gamma: EM wave, stopped by thick lead or concrete.
Key Terms & Definitions
- Isotope — Atom forms with the same number of protons but different numbers of neutrons.
- Radioactive Decay — Spontaneous process where unstable nuclei emit particles/rays to become more stable.
- Alpha Particle — Helium nucleus (2 protons, 2 neutrons), +2 charge.
- Beta Particle — High-speed electron emitted from the nucleus, -1 charge.
- Gamma Ray — Electromagnetic radiation emitted by the nucleus, no charge/mass.
- Ionizing — Ability of radiation to knock electrons off atoms.
- Penetration — How far radiation can travel through material.
Action Items / Next Steps
- Review properties and uses of each type of nuclear radiation.
- Prepare for questions comparing ionizing and penetrating abilities of alpha, beta, and gamma radiation.