Nuclear Reactions & Radioactivity
Nuclear reactions involve changes to the nucleus of atoms, releasing enormous amounts of energy through processes such as radioactive decay, fission, and fusion.
What You Need to Know
Key Concept Diagram
Radioactive decay occurs when an unstable nucleus emits radiation (alpha, beta, or gamma) to become more stable
Alpha particles (helium nuclei) have low penetration but high ionisation; beta particles (electrons) are more penetrating; gamma rays are electromagnetic and most penetrating
Nuclear fission splits a heavy nucleus (e.g., uranium) into smaller nuclei, releasing energy — the basis of nuclear power
Nuclear fusion joins light nuclei (e.g., hydrogen isotopes) into a heavier nucleus, releasing far more energy — the process powering the Sun
Key Vocabulary
Radioactive decay
The spontaneous emission of radiation from an unstable atomic nucleus as it transforms into a more stable state
Half-life
The time required for half of the radioactive nuclei in a sample to decay
Nuclear fission
The splitting of a heavy atomic nucleus into two smaller nuclei, releasing large amounts of energy and neutrons
Nuclear fusion
The combining of two light atomic nuclei to form a heavier nucleus, releasing enormous amounts of energy
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
Which type of nuclear radiation is stopped by a sheet of paper?
Question 2
A radioactive sample has a half-life of 10 years. If you start with 80 g, how much remains after 30 years?
Question 3
Nuclear fusion is the process that powers stars like our Sun. What does fusion involve?
Key Concepts Summary
- ●Radioactive decay occurs when an unstable nucleus emits radiation (alpha, beta, or gamma) to become more stable
- ●Alpha particles (helium nuclei) have low penetration but high ionisation; beta particles (electrons) are more penetrating; gamma rays are electromagnetic and most penetrating
- ●Nuclear fission splits a heavy nucleus (e.g., uranium) into smaller nuclei, releasing energy — the basis of nuclear power
- ●Nuclear fusion joins light nuclei (e.g., hydrogen isotopes) into a heavier nucleus, releasing far more energy — the process powering the Sun