Radioactivity
1. The diagram shows emissions from a source passing into the electric field between two charged plates.
What is emitted by this source?
A neutrons and γ-rays only
B α-particles and β-particles only
C α-particles and γ-rays only
D β-particles and γ-rays only
2. Which row in the table describes the process of nuclear fusion and identifies the change in total mass of
the particles involved?
3. A scientist was asked to separate the following equations into two categories: nuclear fission and nuclear
fusion.
Which equations show nuclear fission?
A 1 and 2
B 1 and 3
C 1 and 4
D 2 and 4
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4. How do the sizes of the two nuclei produced in a nuclear fission reaction compare to the size of the
original nucleus?
A both larger than the original nucleus
B one larger and one smaller than the original nucleus
C both smaller than the original nucleus
D one smaller and one the same size as the original nucleus
5. Which statement about the radioactive decay of a substance is correct?
A It cannot be predicted when a particular nucleus will decay.
B Placing a radioactive substance inside a lead-lined box prevents it from decaying.
C The decay always produces poisonous gases.
D The rate of decay increases if the substance is dissolved in water.
6. Carbon-14 has a proton number (Z) of 6 and a nucleon number (A) of 14.
Nitrogen-14 has a proton number of 7 and a nucleon number of 14.
Carbon-14 emits β-particles to form nitrogen-14.
Which nuclide equation describes this process?
7.
8. Some radioactive nuclei decay to give new nuclei which are also radioactive. Part of a series of decays is
shown.
How many decays involve the emission of a
A1
B2
C3
-particle?
D5
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9. The graph shows the activity of a radioactive source over a period of time.
What is the half-life of the source?
A 1.0 minute
B 2.0 minutes
C 2.5 minutes
D 4.0 minutes
10. A scientist uses a counter to measure the radioactivity of a sample of nitrogen-13.
The counter and sample of nitrogen-13 are on a table in a laboratory.
The reading on the counter is recorded for a period of 80 min and a graph is drawn using the
measurements.
What is the best estimate for the half-life of the sample of nitrogen-13?
A 10 min
B 12 min
C 14 min
D 40 min
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11. A radioactive source has a half-life of 0.5 hours.
A detector near the source shows a reading of 6000 counts per second.
Background radiation can be ignored.
What is the reading on the detector 1.5 hours later?
A 750 counts per second
B 1500 counts per second
C 2000 counts per second
D 3000 counts per second
12. A radioactive material has a half-life of 20 days.
A sample of the material contains 8.0 × 1010 atoms.
How many atomic nuclei have decayed after 60 days?
A 1.0 × 1010
B 4.0 × 1010
C 6.0 × 1010
D 7.0 × 1010
13. A thin sheet of paper is placed between a radioactive source and a radiation detector. The count rate falls
to a very low reading.
From this result, which type of radiation is the source emitting?
A α-particles
B β-particles
C γ-rays
D X-rays
14. Uranium-235 can undergo nuclear fission in many ways.
Which equation correctly shows a possible fission reaction for uranium-235?
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15. The diagram shows a piece of apparatus used to determine the nature of the emissions from a
radioactive source. The absorbers can be raised out of or lowered into the path of the radiation
from the source to the detector. The apparatus is evacuated.
The table gives a set of results for a particular radioactive source.
Which types of radiation are being emitted by the radioactive source?
A α-particles and β-particles
B α-particles only
C β-particles and γ-rays
D β-particles only
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(a) (i)
An americium (Am) nucleus decays by the emission of an α-particle into a neptunium
(Np) nucleus.
Complete the nuclear equation for this decay.
241
Am
95
(ii)
→
[2]
Americium is used in smoke detectors.
Explain why beta (β) emitters or gamma (γ) emitters are not used in smoke detectors.
...........................................................................................................................................
...................................................................................................................................... [1]
(b) The half-life of this americium nuclide is 470 years. A sample of this nuclide contains
8.0 × 1014 atoms. After some time, 6.0 × 1014 americium atoms have decayed.
Calculate the time required for this decay.
time = .......................................................... [3]
[Total: 6]
(c) A radioactive isotope has a half-life of 6.0 years.
A sample of this isotope has a mass of 12 mg.
Calculate the mass of this isotope that remains in the sample after 18 years.
mass remaining = .................................................... mg [3]
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Two of the isotopes of hydrogen are hydrogen-2 ( 12H ) and hydrogen-3 ( 13H ).
(a) (i)
State one similarity in the composition of their nuclei.
..................................................................................................................................... [1]
(ii)
Describe how a nucleus of hydrogen-3 differs from a nucleus of hydrogen-2.
...........................................................................................................................................
..................................................................................................................................... [2]
(b) In a nuclear fusion reactor, a nucleus of hydrogen-2 fuses with a nucleus of hydrogen-3 at
an extremely high temperature. This fusion reaction produces an isotope of element X and
releases a neutron.
(i)
Explain why an extremely high temperature is needed when forcing these two nuclei
together.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [3]
(ii)
Using nuclide notation, complete the equation for this reaction.
2
1H
+
3
1H
[2]
[Total: 8]
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(a) A student investigates a radioactive substance in a laboratory.
Fig. 3.1 is a graph showing the count rate detected as the substance decays for 7.5 minutes.
count rate
counts / min
250
200
150
100
50
0
0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
time / min
Fig. 3.1
The background radiation is 20 counts / min.
(i)
Determine the half-life of the substance.
half-life = ......................................................... [3]
(ii)
Calculate the count rate detected at time = 9.6 minutes.
count rate = .......................................counts / min [2]
(b) The substance emits α-particles and γ-rays. The student suggests that it is safe to store the
substance in a plastic container of thickness 2 mm.
State and explain whether the student’s suggestion is correct.
statement ..................................................................................................................................
explanation ...............................................................................................................................
............................................................................................................................................. [3]
[Total: 8]
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(a) A radioactive nucleus of uranium-235 decays to a nucleus of thorium and emits an α-particle.
Complete the equation.
235
92 U
.......
.......
Th +
4
2α
[2]
(b) A nucleus of uranium-235 undergoes nuclear fission in a reactor.
(i)
State what is meant by nuclear fission.
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[1]
(ii)
Suggest why a nuclear reactor is surrounded by thick concrete walls.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
.......................................................................................................................................[2]
(iii)
State one environmental advantage and one environmental disadvantage of using a
fission reactor to generate electrical energy in a power station.
advantage .........................................................................................................................
...........................................................................................................................................
disadvantage .....................................................................................................................
...........................................................................................................................................
[2]
(c) The thorium produced by the decay in (a) is also radioactive and has a half-life of 26 hours.
At a certain time, a pure sample of this isotope initially contains 4.8 × 109 atoms.
Calculate the number of atoms of this sample that decay in the following 52 hours.
number = ...........................................................[3]
[Total: 10]
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(a) The magnitude of the charge on a β (beta)-particle is 1.6 × 10–19 C.
(i)
State the proton number and nucleon number of an α (alpha)-particle.
proton number ...................................................................................................................
nucleon number ................................................................................................................
[2]
(ii)
Determine the magnitude of the charge of an α (alpha)-particle.
charge ...............................................................................................................................
[1]
(b) A nucleus of radium-230 consists of 88 protons and 142 neutrons. Radium-230 is radioactive
and decays by β (beta)-emission to an isotope of actinium. The symbol for radium is Ra and
the symbol for actinium is Ac.
Write down the nuclide equation for this decay.
[3]
(c) The half-life of radium-230 is 93 min. A sample contains 9.6 × 10–12 g of radium-230.
Calculate the mass of radium in the sample after 279 min.
mass = ......................................................... [2]
[Total: 8]
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