New
New
Year 11
OCR
Higher
Radioactive half-life
I can describe the random nature of radioactive decay and the predictability of radioactive half-life.
New
New
Year 11
OCR
Higher
Radioactive half-life
I can describe the random nature of radioactive decay and the predictability of radioactive half-life.
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Lesson details
Key learning points
- Radioactive decay is a random process.
- It is impossible to predict the moment that a particular unstable nucleus will decay.
- It is possible to predict how long it will take for half of a sample of a radioactive isotope to decay.
- Radioactive half-life is the time taken for half of a radioactive isotope to decay (or for its activity to halve).
- Each radioactive isotope has its own half-life that is always the same.
Keywords
Random - to happen entirely by chance
Radioactive decay - a random process by which unstable nuclei emit radiation
Decay curve - shows the pattern in radioactive decay for a large set of identical unstable nuclei
Radioactive half-life - the time taken for half the nuclei of a radioactive isotope to decay
Common misconception
Most pupils have difficulty in truly understanding randomness.
Use analogies to explain randomness.
If the relevant health and safety rules are followed, midget gems are good for making half-life graphs. The sweets are eaten if they land on a flat side and are eaten - decaying into another substance. Different brands have different half-lives.
Teacher tip
Equipment
Large number of 6 sides dice, tray, optional: 8 sides dice to compare.
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
This content is © Oak National Academy Limited (2025), licensed on
Open Government Licence version 3.0
except where otherwise stated. See Oak's terms & conditions (Collection 2).Lesson video
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Starter quiz
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6 Questions
Q1.
Which of the following describe what a radioactive isotope is?
An atom with a stable nucleus that does not change over time.
An atom that does not emit any radiation and remains unchanged.
Q2.
What happens to a nucleus when it undergoes radioactive decay?
It only emits energy.
It only emits particles.
It splits into two smaller nuclei.
Q3.
Radioactive decay is the process where …
a larger nucleus splits into two smaller nuclei.
an atom loses its outer shell electrons to form an ion.
two smaller nuclei combine to form a larger nucleus.
Q4.
Which of the following methods can an unstable nucleus use to decay?
alpha decay
beta decay
gamma decay
Q5.
Which of the following are random events?
The temperature at which pure ice melts.
The temperature at which pure water boils.
Q6.
The decay of a radioactive isotope is a random process. This means that we cannot predict …
which element an unstable nucleus will decay into.
which type of radiation an unstable nucleus will emit.
Exit quiz
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6 Questions
Q1.
Which of the following definitions describing the half–life of a radioactive isotope is correct?
Half the time it takes for one nucleus to decay.
Half the time it takes for the number of nuclei to fall to zero.
Q2.
Which of the following factors affects the half–life of a radioactive substance?
the temperature of the environment
the pressure of the environment
the chemical form of the substance
Q3.
Which of the following statements about the half–life of radioactive isotopes are correct?
Half–life does not depend on the radioactive isotope.
All radioactive isotopes have the same half–life.
Q4.
Starting with the shortest, sort the following radioactive isotopes into order of increasing half-life.
Q5.
Two radioactive isotopes of uranium are uranium–235 (U–235) and uranium–238 (U–238). Which of the following statements about their half–lives is correct?
U–238 and U–235 have the same half–life.
U–238 has a much shorter half–life than U–235.
The half–life of each depends on chemical properties, not nuclear properties.
Q6.
A radioactive isotope has a half–life of 5 minutes. Match each of the following amounts of the sample remaining to the correct amount of time that has passed.
0 mins
5 mins
10 mins
15 mins
20 mins