Nuclear equations

Carbon-14 is a radioactive substance that emits beta minus (β^–) particles.

Which of these is the unit for the activity of a sample of carbon-14?

Which row of the table gives a correct comparison of the penetrating abilities of alpha, beta and gamma radiation?

The mass of a beta minus particle is 9.1 × 10^–31kg.

Calculate the kinetic energy of a beta minus particle moving with a speed of 3.8 × 10⁶m / s.

kinetic energy =_........

Describe what happens in the nucleus of an atom when a beta plus particle is emitted.

*(c) Radioactive decay can produce gamma radiation and alpha radiation.

Compare the processes of gamma decay and alpha decay.

Your answer should include

• a description of both gamma radiation and alpha radiation

• the effect of each type of decay on the original nucleus.

Figure 12 is a diagram representing an atom.

Write the names of the particles X, Y and Z on the lines next to each letter in Figure 12.

The nucleus of a different atom emits a gamma ray.

What happens to the number of particles in the nucleus?

A teacher demonstrates a radioactivity experiment to a class of students.

The teacher places a radioactive source in front of a radiation detector.

State one safety precaution the teacher should take.

The teacher uses the detector to measure the activity of the source several times.

Figure 13 shows the results.

The teacher tells the class that radioactive decay is random.

State how the data in Figure 13 supports this statement.

Calculate the mean of the four measurements in Figure 13.

The teacher moves the radiation detector to different distances from the radioactive source.

The teacher determines the mean detector reading at each distance from the source.

The teacher plots the results on graph paper, as shown in Figure 14.

The source emits alpha radiation only.

Explain how the graph in Figure 14 shows that the source only emits alpha radiation.

Give a reason why the mean detector reading in Figure 14 does not fall to zero in this experiment.

An electron has a charge of –1.

The charge on an alpha particle is

Alpha, beta and gamma are all ionising radiations.

Give the meaning of the term ionising.

A teacher determines the background radiation count rate in a laboratory.

Explain how to determine a value for the background radiation count rate.

The teacher now investigates the absorption of beta radiation by different thicknesses of aluminium.

The apparatus available is

• a source of beta radiation

• a Geiger–Müller (G-M) tube and counter

• 10 pieces of aluminium, each 0.5 mm thick

• a metre rule.

Sketch a labelled diagram showing the positions of the apparatus when the measurements are being taken.

Give the independent variable in this investigation.

Name a quantity that must be kept constant during the investigation.

Strontium-90 is the source of beta minus radiation in this investigation.

Complete the nuclear equation for this emission of beta minus radiation.

Figure 11 is the symbol for a nucleus of americium-241.

Figure 11

Americium-241 is a radioactive isotope of americium.

Americium-241 decays by emitting alpha (α) particles.

Which of these is the symbol for another radioactive isotope of americium?

Which of these is the approximate maximum distance that alpha particles can travel in air at normal atmospheric pressure?

Complete the equation in Figure 12 for americium-241 decaying into neptunium (Np).

Figure 12

The activity of a radioactive source is measured as 128 Bq.

This is shown as a point on the graph in Figure 13.

The half-life of this radioactive source is 17 s.

Use this information to plot three more points on the graph grid in Figure 13 to show how the activity of the source changes with time.

Describe what happens in the nucleus of an atom when a positron is emitted.

Sometimes food can become contaminated with radioactive substances.

Describe the harmful effects of eating food contaminated with radioactive substances.

Gamma radiation can be used in food processing to irradiate food.

Explain why some food is irradiated with gamma radiation.

Gamma radiation is part of the electromagnetic spectrum.

When the nucleus of an atom emits a gamma ray, the number of protons in the nucleus and the number of neutrons in the nucleus do not change.

State how the nucleus does change when it emits a gamma ray.

*(d) Gamma radiation is produced by radioactive decay.

Alpha radiation and beta radiation are also produced by radioactive decay.

Compare the processes of alpha decay and beta decay.

Your answer should include what each radiation is and what effect each decay has on the original nucleus.

Which of these describes isotopes of an element?

Figure 9 represents a decay that can happen inside the nucleus of an atom.

Which decay is represented in Figure 9?

The half-life of cobalt-60 is 5 years.

A school cobalt source had an activity of 38.5 kBq in the year 2000.

Estimate the activity of this source in the year 2020.

Explain what can happen to the body if a person has a prolonged exposure to gamma rays.

A G-M tube is connected to a counter. A teacher places the G-M tube near to a radioactive source. A student starts the counter and clock at the same time and writes down the readings shown on the counter every 15 s.

The student plots the readings with a line of best fit, as shown in Figure 10.

Calculate the average count rate, in counts / s, from the graph.

Show your working on the graph.

average count rate =_........ counts / s

The student says that the experiment must have been done carelessly because the data seemed quite scattered away from the best fit line.

The teacher claims such results should be expected in radioactivity experiments.

Justify the teacher’s claim.

Carbon‑13 and carbon‑14 are isotopes of carbon.

Nuclei of carbon‑13 and carbon‑14 can be represented by these symbols

13 14

Complete the table for an atom of carbon‑13 and an atom of carbon‑14.

State the name of an instrument that can be used to measure radioactivity.

State two sources of background radiation.

Carbon‑14 is radioactive and has a half‑life of 5 700 years.

The number of radioactive carbon‑14 atoms in a very old piece of wood is found to have decreased from 1 000 000 to 125 000.

Determine the age of the piece of wood.

Carbon‑14 decays into nitrogen‑14.

The symbol for nitrogen‑14 is¹⁴₇N

Explain what happens in a carbon‑14 nucleus when it decays to a nitrogen‑14 nucleus.

Figure 4 shows a Geiger-Müller (GM) tube used for measuring radioactivity.

Figure 4

Describe how a teacher should use a Geiger-Müller (GM) tube to compare the count-rates from two different radioactive rocks.

A hospital uses a radioactive isotope with a half-life of 6 hours.

A technician measures a count rate of 80 counts per minute (cpm) from this isotope.

Complete the graph on Figure 5, as accurately as possible, to show how the count-rate from this isotope will change from the time of the first measurement.

The first point is already drawn in Figure 5.

One radioactive source used in hospitals is technetium (Tc).

Technetium is produced from the radioactive decay of molybdenum (Mo).

Complete the following nuclear equation.