2 min read
Radioactivity
Radioactivity is the spontaneous and random emission of radiation from an unstable atomic nucleus.
Choose Your Level
Radioactivity
Some atomic nuclei are unstable.
They can change by giving out radiation.
We cannot predict the exact moment one nucleus will decay, but we can study large groups of nuclei using probability.
Recommended for Class 10
Radioactivity
Radioactivity is the spontaneous and random emission of radiation from an unstable atomic nucleus.
An unstable nucleus changes into a more stable state by emitting nuclear radiation.
The main types studied at this level are:
alpha (α) beta (β) gamma (γ)
Spontaneous
Radioactive decay happens naturally without needing an external trigger.
Random
It is impossible to predict exactly when a particular unstable nucleus will decay.
However, for a very large number of nuclei, the overall behaviour can be described statistically.
Nuclear Change
Radioactivity involves changes in the nucleus, not ordinary chemical changes in electron arrangement.
Activity
The activity of a radioactive sample tells how many nuclear decays occur per second.
The SI unit is:
becquerel (Bq)
**1 Bq = 1 decay per second**
Background Radiation
People are naturally exposed to small amounts of radiation from sources such as:
rocks and soil; cosmic radiation; some materials in the environment; medical procedures when used.
Radioactivity — Advanced
Radioactive decay is a stochastic nuclear process. Individual decay events are unpredictable, but large populations follow well-defined statistical decay laws.
Common Mistakes
Common Mistakes
- Mistake
Radioactive decay is not caused by heating the sample.
- Mistake
A radioactive nucleus does not decay because it has “run out of electrons.”
- Mistake
Radioactivity is a nuclear process.
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
Radioactivity → spontaneous + random nuclear decay.
Activity → decays per second.
Unit → Bq.
- Definition
Did you understand this topic?
Your answer is saved with your learning record. It does not mark the topic as mastered.
Ready to test yourself?
You've completed the learning section.
Practice
PQ
Q1. Define radioactivity.
PQ
Q2. What does spontaneous mean?
PQ
Q3. What does random mean?
PQ
Q4. Define activity.
PQ
Q5. State the SI unit of activity.
Exam Practice
EQ
Q1. Define radioactivity.
EQ
Q2. Explain why radioactive decay is described as spontaneous.
EQ
Q3. Explain why radioactive decay is random.
EQ
Q4. Define activity and state its unit.
EQ
Q5. Give two sources of background radiation.
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.