Atomic StructureDefinitions

Key Definitions

Part of Half-Life · GCSE GCSE Physics revision

This definitions covers Key Definitions within Half-Life for GCSE Physics. Revise Half-Life in Atomic Structure for GCSE Physics with 15 exam-style questions and 23 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 7 of 13 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.

Topic position

Section 7 of 13

Practice

15 questions

Recall

23 flashcards

📖 Key Definitions

Half-life: The time taken for the number of radioactive nuclei in a sample (or the activity of the sample) to halve.

Activity: The number of nuclear decays per second, measured in becquerels (Bq). 1 Bq = 1 decay per second.

Count rate: The number of radiation counts detected per unit time (often per minute or second). Related to, but not equal to, activity.

Becquerel (Bq): The SI unit of radioactivity. 1 Bq = 1 nuclear decay per second.

Keep building this topic

Read this section alongside the surrounding pages in Half-Life. That gives you the full topic sequence instead of a single isolated revision point.

How It Works: Why the Curve Is Exponential Common Misconceptions ⏳ Counting Down the Atoms Understanding Half-Life

Practice Questions for Half-Life

What is the definition of half-life?

A. The time taken for all of the radioactive nuclei to decay
B. The time taken for half of the radioactive nuclei in a sample to decay
C. The time taken for the activity of a sample to double
D. Half of the time for a nucleus to become stable

1 markfoundation

Explain what is meant by saying radioactive decay is 'random and spontaneous'.

2 marksstandard

Quick Recall Flashcards

What is half-life?

Half-life is the time taken for half the unstable nuclei in a radioactive sample to decay, or the time for the activity of a radioactive source to fall to half its original value.

Why is radioactive decay described as random?

Radioactive decay is random because we cannot predict when any individual nucleus will decay. We can only predict the probability of decay and the average behaviour of large numbers of nuclei.

15 questions on Half-Life — practise free

Instant marking, adaptive difficulty, and 23 spaced repetition flashcards. Free until your GCSEs.

Try PrepWise Free

How It Works: Why the Curve Is Exponential

Common Misconceptions