Radioactive Decay: Alpha, Beta and Gamma
An unstable nucleus throws out an alpha particle, a beta particle or a gamma ray, and each has its own range and stopping material. A nuclear equation tracks how the mass number and atomic number change.
What a learner can do afterwards
- Names what each emission is made of and what absorbs it, from paper to lead
- Completes a nuclear equation for alpha and beta decay with mass and atomic numbers balanced
- Explains why an alpha emitter is the most dangerous kind to swallow but the least dangerous at arm's length
1 · Read
Some nuclei are unstable and rearrange themselves with no push from outside. They throw out three families. Alpha particles are chunky helium nuclei that ionise fiercely but stop in paper or skin. Beta particles are fast electrons that cross metres of air and need aluminium. Gamma rays are pure energy waves that need thick lead or concrete.
A nuclear equation is strict bookkeeping. The top mass numbers must balance and the bottom atomic numbers must balance across the arrow. In alpha decay the mass number drops by 4 and the atomic number drops by 2. In beta decay the mass number stays put while the atomic number rises by 1. Gamma changes neither.
Omar checks an alpha equation. He reads the parent numbers, subtracts 4 on top and 2 below, and names the daughter that is left. Then he adds both columns on each side. If either column fails to balance, he knows the equation is wrong.
The danger ranking flips with distance, which catches many learners out. An alpha emitter you swallow sits against living tissue and hammers it, making it the worst internal hazard. At arm's length the same source cannot cross skin, while gamma still reaches you.
Name each emission, balance its equation, match its stopper.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.