Nuclear equations

Different radioactive isotopes emit different types of radiation.

One isotope of uranium (U) decays into thorium (Th) by emitting an alpha particle (He).

Which nuclear equation shows the decay of this isotope of uranium?

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Figure 4 shows how the percentage of uranium atoms in a sample of one uranium isotope varies with time.

What is the time taken for 50% of the atoms of this uranium isotope to decay?

Use Figure 4.

What is the half-life of this uranium isotope?

Figure 5 shows how the percentage of uranium atoms varies with time for three different isotopes of uranium, A, B and C.

Figure 5

Which isotope is the most unstable?

Give a reason for your answer.

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Figure 6 shows the nuclei of four different atoms.

Which nucleus in Figure 6 has the smallest mass number?

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Which nucleus in Figure 6 has an atomic number of 4?

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Which two nuclei in Figure 6 are isotopes of the same element?

Give a reason for your answer.

Scientists have replaced old models of the atom with newer models.

The nuclear model of the atom has a nucleus at the centre.

Which model of the atom was replaced by the nuclear model?

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What does the nuclear model state about the mass of an atom?

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Some atoms emit radiation.

Why do scientists sometimes change the model used to describe the structure of the atom?

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When radioactivity was discovered, the dangers of radiation were not known.

Some scientists were irradiated and contaminated while working with the radioactive materials.

Describe the difference between irradiation and radioactive contamination.

Polonium-210 was one of the first radioactive elements to be discovered.

Polonium-210 (Po) decays into lead (Pb).

Complete the nuclear equation for polonium-210.

Polonium-210 has a half-life of 138 days.

A sample of polonium contains 256 000 atoms.

Calculate the time taken for the number of polonium-210 atoms to reach 16 000.

A sample of polonium contains equal numbers of polonium-209 atoms and polonium-210 atoms.

Polonium-209 has a half-life of 125 years.

Polonium-210 has a half-life of 138 days.

Explain how the activity of polonium-209 compares with the activity of polonium-210 in this sample.

Radioactive isotopes emit different types of nuclear radiation.

What does an alpha particle consist of?

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What is a beta particle?

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A krypton (Kr) nucleus decays into a rubidium (Rb) nucleus by emitting a beta particle.

What is the correct equation for this decay?

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Figure 5 shows an experiment to demonstrate how alpha, beta and gamma radiation penetrate different materials.

The experiment takes place in a vacuum.

Three different materials are used:

• a sheet of paper

• a 0.5 cm thick sheet of aluminium

a 10 cm block of lead.

Each material is placed one at a time between the radioactive source and the GM tube.

The GM tube and counter show whether the material has stopped the radiation.

Complete Table 1 to show how alpha, beta and gamma radiation penetrate the materials in Figure 5.

Use the words Yes and No.

Part of Table 1 has been completed for you.

Alpha, beta and gamma radiation have different ionising powers.

Draw one line from each radiation type to the correct ionising power.

Some sources of background radiation are natural and other sources are man-made.

Which of the following is a man-made source of background radiation?

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The average background radiation dose per year in the UK is 2.0 millisieverts.

A dental X-ray gives a patient a radiation dose of 0.005 millisieverts.

Calculate how many dental X-rays would be the same as the average background radiation dose per year.

Complete the nuclear equation for this decay by writing the missing number in each box.

Explain how the risk from internal contamination is different to the risk from external irradiation by a source of alpha radiation.

Atoms of different elements have different properties.

Which of the following is the same for all atoms of the same element?

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Which of the following is different for isotopes of the same element?

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A nucleus emits radiation.

Figure 7 shows how the mass number and the atomic number change.

The nucleus is labelled D.

Which type of radiation is emitted when nucleus D decays?

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Nucleus E also emits radiation.

Figure 8 shows how the mass number and the atomic number change for nucleus E.

Which type of radiation is emitted when nucleus E decays?

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Beta radiation can be used to monitor the thickness of paper during production.

Figure 9 shows how the radiation is used.

The computer uses information from the radiation detector to change the size of the gap between the rollers.

Complete the sentences.

Choose answers from the box.

Each answer can be used once, more than once or not at all.

The thickness of the paper between the beta source and the detector increases.

This is because the amount of radiation absorbed by the paper

All radioactive elements have a half-life.

What is meant by ‘half-life’?

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Why should the radiation source used in Figure 9 have a long half-life?

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Figure 6 shows the mass number and the atomic number for the nuclei of five different atoms.

How many neutrons are there in a nucleus of atom A ?

Which two atoms in Figure 6 are the same element? Tick (✓) one box.

Nucleus B decays by emitting an alpha particle. Draw an arrow on Figure 7 to represent the alpha decay.

What is meant by the ‘random nature of radioactive decay’?

A polonium (Po) nucleus decays by emitting an alpha particle and forming a lead (Pb) nucleus. Po → Pb + α The lead (Pb) nucleus then decays by emitting a beta particle and forms a bismuth (Bi) nucleus. Pb → Bi + β The bismuth (Bi) nucleus then decays by emitting a beta particle and forms a polonium (Po) nucleus. Bi → Po + β

Explain how these three decays result in a nucleus of the original element, polonium.

Radioactive waste from nuclear power stations is a man-made source of background radiation.

Which of the following is also a man-made source of background radiation? Tick (✓) one box.

Nuclear power stations use the process of nuclear fission. Complete the sentences to describe the process of nuclear fission. Choose answers from the box.

Plutonium-239 is one type of radioactive waste from nuclear power stations. The following nuclear equation represents the decay of plutonium-239 (Pu-239). 239 235 4

How does the nuclear equation show that alpha radiation is emitted when plutonium-239 decays?

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Figure 8 shows how the activity of a sample of plutonium-239 varies with time.

How much time will it take for the activity of the sample of plutonium-239 to fall to half of its initial activity?

What is the half-life of plutonium-239?

The radioactive waste from a nuclear power station is buried underground. People are warned to stay away from places where radioactive waste is buried. Suggest one risk of going near the place where radioactive waste is buried.

Polonium-210 is a radioactive isotope that decays by emitting alpha radiation.

Which is the correct decay equation for polonium-210?

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Why is alpha radiation dangerous inside the human body?

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Figure 3 shows how the mass of a sample of polonium-210 changes with time.

Determine the change in mass of the sample of polonium-210 between 50 and 150 days.

Estimate the mass of polonium-210 remaining after 300 days.

Nuclear radiation can cause ionisation. Complete the sentences. Choose answers from the box.

The resulting ion has charge.

Polonium-210 is a radioactive isotope that decays by emitting alpha radiation.

Complete the decay equation for polonium-210

Explain why contamination of the inside of the human body by a radioactive material that emits alpha radiation is highly dangerous.

A sample of polonium-210 was left for 414 days.

After this time it had a mass of 1.45 × 10^-4 g

The half-life of polonium-210 is 138 days.

Calculate the initial mass of the sample.