Radioactive decay and nuclear radiation

There are different isotopes of the element lead.

What is the difference between the atoms of different isotopes of lead?

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The isotope lead-210 is radioactive.

What is meant by ‘lead-210 is radioactive’?

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The isotope lead-210 emits beta radiation.

What is beta radiation?

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The paint in an old painting contains the isotope lead-210.

The lead-210 in the paint can be used to estimate the age of the painting.

Figure 1 shows how the activity of the lead-210 in the paint changes with time.

What was the initial activity of the lead-210 in the paint?

Use Figure 1.

Calculate the activity of the lead-210 in the paint after one half-life.

What was the estimated age of the painting when the activity was 10 kBq?

Use Figure 1.

The paint also contains other radioactive substances.

A scientist removed the other radioactive substances before measuring the activity.

The activity would be greater if the other radioactive substances were not removed.

How would the estimate of the age of the painting be different if the activity was greater?

Use Figure 1.

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The other radioactive substances in the paint emit different types of radiation.

Complete the sentence.

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Complete the sentence.

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Three types of radiation emitted by unstable nuclei are:

• alpha particle

• beta particle

• gamma ray.

Describe each type of radiation.

The radioactive isotope gold-198 (Au) decays to mercury (Hg) by emitting beta radiation.

Complete the nuclear equation for the decay of gold-198.

Gold-198 is used in the treatment of cancer.

A small sample containing gold-198 is surgically implanted into a patient, very near to the cancer cells.

Figure 4 shows how the activity of the sample changes after it has been implanted.

Determine the half-life of gold-198.

Determine the percentage decrease in the activity at 5 days.

Give your answer to 2 significant figures.

The sample containing gold-198 is implanted very near to the cancer cells.

Give two reasons why.

After treatment, the sample containing gold-198 is not removed from the patient.

Suggest why the sample is left in the patient and not removed.

Some people used to think that radioactive substances had health benefits.

100 years ago, a company made toothpaste containing the radioactive isotopes radium-228 and radium-226.

Figure 3 shows the symbols for these isotopes.

How are atoms of radium-228 different from atoms of radium-226?

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Figure 4 shows how the activity of a sample of radium-228 changed over time.

What is the approximate half-life of radium-228?

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A scientist investigated whether the toothpaste in four tubes of the 100-year-old

toothpaste is equally radioactive.

Figure 5 shows the equipment used.

When the equipment was arranged as shown in Figure 5, it was not possible to detect alpha particles from the toothpaste.

Suggest how the scientist adjusted the equipment to detect alpha particles from the toothpaste.

The scientist adjusted the equipment and determined the activity of the toothpaste from each tube.

Table 1 shows the results.

What was the range of activities shown in Table 1 ?

What was the independent variable in the investigation?

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What was the dependent variable in the investigation?

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When the toothpaste was new, it caused a risk to health because of the nuclear radiation emitted.

What happened to the risk to health from the toothpaste after 100 years?

Which property makes nuclear radiation hazardous?

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Last century, scientists used evidence from the alpha particle scattering experiment to develop a new model of the atom.

In the experiment, alpha particles were directed towards a piece of gold foil.

What does an alpha particle consist of?

197 A gold atom has the symbol₇₉ Au.

How many neutrons are there in this gold atom?

The alpha particle scattering experiment led to the plum pudding model of the atom being replaced by the nuclear model.

Figure 11 shows the results predicted by the plum pudding model and the actual results from the alpha particle scattering experiment.

Describe how the actual results led to the plum pudding model of the atom being replaced by the nuclear model.

You should include details of the plum pudding model and the nuclear model of the atom.

Scientists did not know that neutrons existed when they first did alpha particle scattering experiments.

Which scientist did the experiments that provided evidence that neutrons exist?

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Last century, scientists used evidence from the alpha particle scattering experiment to develop a new model of the atom.

In the experiment, alpha particles were directed towards a piece of gold foil.

What does an alpha particle consist of?

197 A gold atom has the symbol₇₉ Au.

How many neutrons are there in this gold atom?

The alpha particle scattering experiment led to the plum pudding model of the atom being replaced by the nuclear model.

Figure 2 shows the results predicted by the plum pudding model and the actual results from the alpha particle scattering experiment.

Describe how the actual results led to the plum pudding model of the atom being replaced by the nuclear model.

You should include details of the plum pudding model and the nuclear model of the atom.

Scientists did not know that neutrons existed when they first did alpha particle scattering experiments.

Which scientist did the experiments that provided evidence that neutrons exist?

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A scientist investigated the radiation emitted by different radioactive isotopes.

The scientist had a sample of polonium-210.

The radiation emitted by polonium-210 can be represented by the symbol⁴₂ He.

Which type of radiation can be represented by the symbol⁴₂ He?

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How many protons are there in a particle of radiation represented by⁴₂ He?

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A polonium-210 (Po) nucleus changes into a lead (Pb) nucleus by emitting a ⁴₂ He particle. This is shown by the following nuclear equation. 210 206 4 Po → Pb + He 84 X 2

What is the value of X ?

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The sample of polonium-210 had an activity of 100 Bq.

Complete the sentence.

Choose the answer from the box.

After one half-life, the activity of polonium-210 in the sample

The scientist investigated another radioactive isotope that is a source of gamma

radiation.

Figure 1 shows the equipment used.

The count-rate is the number of counts detected each second.

In 30 seconds the number of counts detected was 1500.

Calculate the count-rate.

The scientist placed a thick sheet of lead between the source of gamma radiation and

the detector.

What was the effect of the sheet of lead on the count-rate?

Give a reason for your answer.

The lead was irradiated by the gamma radiation.

What happened to the lead when it was irradiated by the gamma radiation?

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Gamma radiation is emitted from the nucleus of an atom.

Complete the sentence.

Choose the answer from the box.

Gamma radiation consists of.

Figure 2 shows the scientist holding the radioactive source using tongs.

Suggest one reason why using long tongs rather than short tongs was safer for the scientist.

A scientist investigated a sample of a radioactive material to determine if it would be suitable for medical use.

The method, results and conclusions of the scientist will need to be checked by other scientists before the results of the investigation are published. What name is given to this checking process?

There is an increased risk of cancer if the scientist is irradiated by nuclear radiation. What property of nuclear radiation causes the increased risk of cancer?

The activity of a radioactive source is the rate at which the nuclei of the source decay. What is the unit for the activity of a radioactive source?

The scientist placed a radiation detector near the sample and measured the count-rate. Explain why the count-rate is less than the activity of the sample.

The scientist recorded the count-rate from the sample with the radiation detector at different distances from the sample. Table 2 shows the results.

Explain which type of radiation was emitted by the sample.

The scientist moved the detector closer to the sample and started a stopwatch. The scientist measured the count-rate from the sample at different times. Table 3 shows some of the results.

The scientist realised that 30 minutes is a whole number of half-lives. Calculate the value of X in Table 3.

The scientist had a second sample of the radioactive material. The scientist made appropriate measurements, then calculated the half-life of each sample. Why was the half-life calculated from the second sample slightly different from the half-life calculated from the first sample? Tick (✓) one box.

A teacher demonstrated that the radioactive isotope americium-241 emits alpha particles.

Figure 4 shows the equipment used.

An americium-241 nucleus (Am) emits an alpha particle and turns into a neptunium nucleus (Np).

Which is the correct nuclear equation for this decay?

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What is the furthest distance that alpha radiation can travel in air?

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The teacher placed a piece of paper between the americium-241 and the radiation detector.

The reading on the count rate meter decreased by a large amount.

Why does the decreased reading show that americium-241 emits alpha radiation?

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The teacher replaced the americium-241 with a source of beta radiation.

Which symbol represents a beta particle?

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The count rate from the source was 119 ± 7 counts per second.

Calculate the smallest count rate this could have been.

A teacher investigated how the distance between a different radioactive source and the detector affects the count rate.

Draw one line from each type of variable to the description.

Figure 5 shows how the count rate from the different radioactive source changed with the distance from the source.

Describe the relationship between the distance from the source and the count rate.

A smoke detector contains a source of alpha radiation in a plastic case.

A source of beta radiation in a smoke detector would be more hazardous than a source of alpha radiation. Explain why.

Actinium (Ac) is one source of alpha radiation. An actinium (Ac) nucleus emits an alpha particle (α) and turns into a francium (Fr) nucleus. This can be represented as:

Determine the values of A and Z.

A teacher wanted to find out what nuclear radiation is emitted from a source. The teacher placed different barriers between the source and a detector. The teacher recorded the count for 30 seconds after each barrier was put in place. Table 2 shows the results.

Explain what nuclear radiation was emitted by the source.

Figure 11 shows how the activity of four different radioactive isotopes, A, B, C and D changes over time.

Write the isotopes A, B, C and D in order of increasing stability of their nuclei. Explain your answer.

Least stable Most stable

A radioactive source emits alpha, beta and gamma radiation.

An alpha particle is the same as a helium nucleus.

How many times bigger is the radius of a helium atom than the radius of an alpha particle?

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Alpha particles can ionise atoms in the air.

What happens to an atom when it is ionised by an alpha particle?

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A spark detector is a device that can be used to detect alpha radiation.

A spark detector works by alpha particles ionising atoms in the air near a wire mesh.

A large potential difference creates a spark when the air near the wire mesh is ionised.

Suggest why a spark detector cannot detect beta radiation.

A teacher wants to demonstrate that the radioactive source emits alpha, beta and gamma radiation.

Figure 11 shows the equipment the teacher has.

Describe a method the teacher could use.

A radioactive source emits alpha, beta and gamma radiation.

An alpha particle is the same as a helium nucleus. How many times bigger is the radius of a helium atom than the radius of an alpha particle? Tick (✓) one box.

Alpha particles can ionise atoms in the air. What happens to an atom when it is ionised by an alpha particle? Tick (✓) two boxes.

A spark detector is a device that can be used to detect alpha radiation. A spark detector works by alpha particles ionising atoms in the air near a wire mesh. A large potential difference creates a spark when the air near the wire mesh is ionised. Suggest why a spark detector cannot detect beta radiation.

A teacher wants to demonstrate that the radioactive source emits alpha, beta and gamma radiation. Figure 3 shows the equipment the teacher has.

Describe a method the teacher could use.

Between 1951 and 1992 the USA tested nuclear weapons in a desert.

Complete the sentence. Choose the answer from the box.

Radioactive dust from the nuclear weapons testing settled on the desert. This is

The desert now contains radioactive tritium. Figure 3 shows how the activity of the tritium in a sample taken from the desert changed with time.

The sample was collected from the desert in 1992. Determine the activity of the tritium in the sample in 2007.

How much time did it take for the activity of the tritium in the sample to decrease from 80 Bq to 40 Bq?

What is the half-life of tritium?

The sample started with 45 billion atoms of tritium. After 4 years the sample had 36 billion atoms of tritium. Calculate the percentage of the tritium in the sample that remained after 4 years.

A scientist determined the activity of a sample of tritium every minute for 3 minutes. Table 1 shows the results.

Why do the activity readings in Table 1 vary? Tick (✓) one box.

What safety precaution should scientists take when working with radioactive materials in a laboratory? Tick (✓) one box.

Studies show that children born near the area of the desert containing tritium were more likely to develop cancer. It is important that the results from these studies are checked by other scientists. What is this process called? Tick (✓) one box.

Different radioactive isotopes emit different types of nuclear radiation.

A polonium-210 (Po) nucleus emits an alpha particle (α) and turns into a lead (Pb) nucleus. This can be represented by the equation:

What is the value of A in the equation? Tick (✓) one box.

What is the value of Z in the equation? Tick (✓) one box.

A strontium-89 nucleus (Sr) emits a beta particle (β) and turns into an yttrium nucleus (Y). This can be represented by the equation:

What are the values of A and Z in the equation?

Gamma radiation is another type of nuclear radiation. What does gamma radiation consist of? Tick (✓) one box.

Explain the differences between the properties of alpha, beta and gamma radiations.

Different radioactive isotopes emit different types of nuclear radiation.

A polonium-210 (Po) nucleus emits an alpha particle (α) and turns into a lead (Pb) nucleus. This can be represented by the equation:

What is the value of A in the equation? Tick (✓) one box.

What is the value of Z in the equation? Tick (✓) one box.

A strontium-89 nucleus (Sr) emits a beta particle (β) and turns into an yttrium nucleus (Y). This can be represented by the equation:

What are the values of A and Z in the equation?

Gamma radiation is another type of nuclear radiation. What does gamma radiation consist of? Tick (✓) one box.

Explain the differences between the properties of alpha, beta and gamma radiations.

Protactinium (Pa) is radioactive.

An atom of one isotope of protactinium contains 91 protons and 143 neutrons.

What is the correct symbol for this atom?

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A teacher investigated how the count rate from a sample of protactinium changed over time.

Table 2 shows the results.

Figure 6 shows some of the teacher’s results.

Complete the graph in Figure 6.

Use data from Table 2.

Draw the line of best fit.

How much time did it take for the count rate to change from 200 counts per second to 100 counts per second?

What is the half-life of protactinium?

The nuclear radiation from the protactinium can pass through paper.

This radiation can only be detected up to 1 metre away from the protactinium.

What type of radiation is emitted by the protactinium?

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The teacher read an article about the effects of radiation on the human body.

Why are articles in scientific journals generally more trustworthy than articles in newspapers?

Lanthanum-140 is a radioactive isotope.

A nucleus of lanthanum-140 emits gamma radiation. What happens to the mass number and the charge of the nucleus when

Why is it difficult to detect gamma radiation?

Activity is the rate at which a radioactive source decays. A teacher measured the count-rate from a sample of lanthanum-140 using a Geiger-Muller (G-M) tube. Explain why the count rate was less than the activity of the sample of lanthanum-140

The teacher investigated how the thickness of lead affected the amount of gamma radiation that could pass through it. Figure 6 shows the apparatus.

Explain why the teacher stood as far away from the apparatus as possible.

Table 1 shows the results.

The teacher concluded that the count rate was not inversely proportional to the thickness of lead. Explain why the teacher was correct. Use the data in Table 1.

Lanthanum-140 can also emit beta radiation and change into cerium. Complete the equation showing the decay of lanthanum (La) 140 into cerium (Ce).

There are other isotopes of cerium which are radioactive. Different isotopes of cerium have different half-lives. The half-life of an isotope can be found by studying how the number of atoms changes over time. Figure 7 shows how the number of atoms of cerium-148 in a 120 g sample changes over time.

Determine the ratio of the number of cerium atoms in the sample when it was 100 seconds old compared with when the sample was 350 seconds old. Use data from Figure 7.

Determine the activity of the sample of cerium when the sample was 20 seconds old. Use Figure 7.

Radioactive nuclei can emit alpha, beta or gamma radiation.

Which type of radiation is the most penetrating?

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Which type of radiation is the most ionising?

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Which type of radiation has the longest range in air?

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When radioactive isotopes in the Earth’s crust decay they release energy.

The decay causes the heating of rocks in the crust.

Figure 8 shows the decay of uranium–238 (U–238) into thorium–234 (Th–234).

Figure 8

Complete Table 2 to show the number of neutrons and protons in the nuclei.

Geothermal power stations pump water through heated rocks.

The temperature of the water increases from 20 °C to its boiling point of 100 °C

Calculate the change in thermal energy when the mass of water heated is 150 kg

Specific heat capacity = 4 200 J/kg °C

Use the Physics Equations Sheet.

The Chernobyl disaster was a nuclear accident that happened in 1986 Radioactive isotopes were released into the environment. The radioactive isotopes emitted alpha, beta and gamma radiation.

What is an alpha particle? Tick one box.

Which statement about beta radiation is true? Tick one box.

Which statement about gamma radiation is true? Tick one box.

Table 3 shows the half-lives of two of the radioactive isotopes that contaminated the environment.

A soil sample was taken from the area around Chernobyl in 1986 The soil sample was contaminated with equal amounts of caesium–137 and iodine–131 Explain how the risk linked to each isotope has changed between 1986 and 2018 Both isotopes emit the same type of radiation.

Determine the year when the activity of the caesium–137 in the soil sample will be 1/32 of its original value.