Radioactive decay
An unstable nucleus randomly gives out radiation to become more stable. It cannot be predicted when a single nucleus will decay, and nothing such as heat or pressure changes the rate.
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Analogy
Popcorn in a pan: you cannot tell which kernel pops next, but the whole pan follows a pattern.
In practice
Smoke alarms, nuclear power and medical scans use radioactive materials.
Practice
Flashcards
- Is radioactive decay predictable for one nucleus?No. It is random.
Interview questions
- A radioactive source has a half-life of 3 hours. A sample starts with 64 g of the isotope. How much is left after 12 hours?
- 12 hours is 4 half-lives
- Halve four times: 32, 16, 8, 4
- 4 g of the isotope remains
Questions people ask
Can you predict when an atom will decay?
No. Decay is random for any single nucleus. You can only say how likely it is over a given time. With millions of atoms, though, the overall pattern is very predictable, which is why half-lives can be measured accurately and used in real sums.
What is background radiation?
Background radiation is low-level radiation that is always around us. It comes from rocks, the air (radon gas), cosmic rays from space, food, and medical or nuclear sources. When measuring a sample, scientists subtract the background count from the reading to find the sample's true value.