Half-life

There are different isotopes of the element carbon.

When carbon-14 decays into nitrogen-14, it emits beta radiation.

Complete the equation for the decay of carbon-14.

Carbon-14 has a half-life of 5700 years.

Explain what half-life means.

Alpha particles, beta particles, and gamma rays can penetrate different types and thicknesses of material.

Draw one line from each type of radiation to the type and maximum thickness of material radiation is able to penetrate.

Type of radiation
Type and maximum thickness of material

Describe one similarity and one difference between a nucleus of iodine-127 and a nucleus of iodine-131.

Iodine-131 is radioactive.

The graph shows how the activity of a sample of iodine-131 changes over time.

Use the graph to show that the half-life of iodine-131 is approximately 8 days.

Show your working on the graph.

Iodine-131 is used as a medical tracer and for radiotherapy when treating cancer patients.

A radiologist injects a patient with a dose of iodine-131. The dose has an initial activity of 4.00 MBq.

Calculate the number of days it takes the activity to reduce to 0.25 MBq.

The radiologist wears gloves and a film badge while handling iodine-131.

The film badge contains photographic film which turns dark when exposed to ionising radiation.

Explain how using the gloves and the film badge reduces risks to the radiologist’s health.

Some students design a practical to model radioactive decay.

Which model is correct?

A Throw a coin in the air 100 times and count the number of heads or tails.

B Throw 10 dice in a tray 10 times and add up the scores.

C Throw 100 dice in a tray and remove the ones with a 6 facing up.

D Throw 100 identical wooden blocks in a tray.

This question is about radioactivity.

Some atoms and isotopes of elements are shown.

Which statements are correct for these atoms and isotopes? Tick (✓) three boxes.

Thorium‑234 decays by emitting beta radiation.

What happens to the mass number and charge of a nucleus of thorium‑234 when it decays?

Draw one line from each quantity to what happens.

Why do some atoms emit nuclear radiation?

The diagram shows how the amount of a radioactive element changes over a total of 30 days.

Calculate the half‑life of this radioactive element.

Some students design a practical to model radioactive decay.

Which model is correct?

A Throw a coin in the air 100 times and count the number of heads or tails.

B Throw 10 dice in a tray 10 times and add up the scores.

C Throw 100 dice in a tray and remove the ones with a 6 facing up.

D Throw 100 identical wooden blocks in a tray.

When uranium‑238 decays, it forms isotopes of different elements.

The graph shows part of the decay chain produced when uranium‑238 decays.

Circle two points on the graph which are isotopes of the same element.

Explain how you worked out your answer.

(b) Describe what happens to the atomic number and mass of a nucleus of²³⁴Th as it decays into (i) ²³⁴Pa.

Which type of radiation is emitted when²³⁴Th decays into²³⁴Pa? (ii)

Eventually the isotope²⁰⁶Pb is formed and the decay chain stops. (d)

Explain why the decay chain stops at²⁰⁶Pb.

16* The graph shows how the activity of a radioactive isotope changes with time. The graph can be used to determine the half-life of the isotope.

Explain what is meant by half-life.

Describe how the half-life of this radioactive isotope is measured using a radiation detector. Draw on the graph to support your answer.

This question is about radioactivity.

Which statements about the nucleus of an atom are correct? Tick (✓) two boxes.

The graph shows how the mass of a radioactive element changes with time.

Describe the trend shown by the graph.

In 1986, a nuclear power station exploded in Chernobyl.

The radioactive isotopes caesium-137 (Cs-137) and iodine-131 (I-131) were released.

An old unit of activity is the Curie (Ci).

• The activity of Cs-137 released in the explosion was 2 300 000 Ci.

• 1 Ci = 37 000 000 000 Bq

Calculate the activity of Cs-137 released in Bq. Give your answer in standard form.

Cs-137 emits beta radiation. The table shows some information about this decay.

Use the table to complete the balanced nuclear equation for Cs-137 decay.

*(c) The isotopes I-131 and Cs-137 from Chernobyl contaminated sheep.

The government stopped the movement of contaminated sheep for 26 years.

• If the activity per kilogram of sheep was greater than 1000 Bq / kg, the sheep were contaminated.

• In 1986, the activity per kg of some sheep was greater than 1600 Bq / kg.

• I-131 emits beta radiation.

• Cs-137 emits beta and gamma radiation.

The graphs show how the amount of I-131 and Cs-137 change with time:

Graph for I-131

Graph for Cs-137

Use the graphs to explain why the government stopped the movement of contaminated sheep for 26 years.

Use ideas about half-life and half-life calculations.

This question is about two radioactive isotopes, X and Y.

Isotope X gives out gamma rays.

The charge on the nucleus of isotope X stays the same.

What happens to the mass number of the nucleus?

Isotope X is stored safely in a container.

Suggest a material for the container.

Describe how an object can be irradiated using isotope X.

Equal amounts of isotope Y are placed in a plastic box and in a cardboard box.

Table 11.1 gives information about both boxes.

Which box is best for storing isotope Y ?

Give one reason for your answer using the information in Table 11.1.

The plastic box does not let any of the radiation emitted by isotope Y pass through it.

Which type of radiation does isotope Y emit?

The graph shows how the quantity of isotope Y changes with time.

Complete Table 11.2 using the graph to help you.

Explain why the half-life of isotope Y is 5 days.

X and Y are radioactive isotopes. They emit either alpha particles or beta particles.

Complete Table 14.1 to show what happens to a nucleus of an atom when an alpha particle or a beta particle is emitted.

A scientist measures the half-life of isotope X.

They measure the half-life three times.

Why do they get a slightly different result each time?

After 18 days, the ratio of the activity of X to the initial activity of X is 1:4.

Calculate the half-life of isotope X.

Isotope X only gives out beta particles. Isotope Y only gives out alpha particles.

The scientist measures the activity of one of the isotopes using a Geiger counter.

They then place a material between the isotope and the Geiger counter and record the reading.

Table 14.2 shows their results:

Which isotope are they using?

Give two reasons for your answer.

The scientist accidentally places isotope X close to isotope Y.

Explain why isotope Y is irradiated, but not contaminated, by isotope X.

Nuclear power is non-renewable and the plants can produce nuclear waste.

Suggest two reasons why some countries still use nuclear power.

A scientist measures the activity of a radioactive isotope. She uses a Geiger-Muller tube connected to a counter.

Table 12.1 shows her results.

What is the mean activity of the isotope?

Is there a pattern in the results in Table 12.1 ?

Explain your answer using ideas about radioactivity.

Carbon-12 is a stable isotope. Carbon-14 is an unstable radioactive isotope.

Table 12.2 shows the contents of each nucleus.

Explain why carbon-12 and carbon-14 are isotopes.

This is the equation for the radioactive decay of carbon-14:

What happens to the nuclear mass (mass number) when carbon-14 decays?

Americium-241 is a radioactive isotope used in smoke alarms.

Table 12.3 shows how the activity of americium-241 changes.

What is meant by the half-life of an isotope?

Use the data in Table 12.3 to calculate the half-life of americium-241.

This is a diagram of a smoke alarm.

Smoke enters the smoke alarm, which blocks the radiation emitted by the americium-241.

A smoke alarm company decides to use a different isotope.

Table 12.4 shows the three choices of isotope.

Which isotope, A, B or C, is the best to use in a smoke alarm?

Tick (✓) one box.

Explain your answer using the information in Table 12.4.

Carbon-12 is a stable isotope. Carbon-14 is an unstable radioactive isotope.

Describe what is meant by the term isotope.

This is the equation for the radioactive decay of carbon-14:

Which type of radiation is emitted by carbon-14?

Describe how the mass and charge of the nucleus changes when the carbon-14 decays.

Mass........

Charge........

Carbon-14 can be used to date ancient objects.

An ancient object is 17 100 years old. The half-life of carbon-14 is 5700 years.

For the ancient object, what is the ratio of the original amount of carbon-14 to the amount of carbon-14 left?

Describe the difference between mean, mode and median.

In your answer use data from the second throw in the table (shaded in grey).

Use the table to estimate the half-life of the dice.

Give your answer to the nearest whole number.

Half-life =........ throws

Describe the difference between mean, mode and median.

In your answer use data from the second throw in the table (shaded in grey).

Use the table to estimate the half-life of the dice.

Give your answer to the nearest whole number.

Half-life =........ throws

This question is about nuclear radiation.

Q and R are different radioactive isotopes. Q has a different half-life to R.

Explain what is meant by the term half-life.

The graph shows how activity of isotope Q and isotope R change with time.

Which isotope, Q or R, has the longest half-life? Explain your answer.

The table shows information about different elements.

Iodine-131 is a radioactive isotope. Iodine-131 decays, emitting a beta () particle.

Write a balanced nuclear equation for iodine-131 decay. The first part is done for you.

The table shows how the activity of iodine-131 decreases with time.

Use your answer to (c)(i) to calculate the half-life of iodine-131.