EXERCISES
_ _ 12. the stepwise disintegration of a radioactive nucleus until a stable nuclide is reached
_ _ 13. the relationship of a decaying nuclide and the resulting nuclide that is produced
_ _ 14. the number of radioactive nuclei in a sample that disintegrate in a given period of
time, for example, 500 dpm
_ _ 15. the amount of time required for 50% of the radioactive nuclei in a given sample
to decay
_ _ 16. an atom whose nucleus is unstable and decays radioactively
_ _ 17. the conversion of one element to another by a nuclear reaction
_ _ 18. a nuclear reaction in which a nucleus splits into two or more lighter nuclei
_ _ 19. a fission reaction in which the neutrons released initiate a second reaction, which in
turn initiate a third reaction, and so on
_ _ 20. the minimum mass of a fissionable nuclide necessary to sustain a chain reaction
_ _ 21. a nuclear reaction in which two light nuclei combine into a single nucleus
_ _ 22. the nuclide of hydrogen having one neutron
_ _ 23. the nuclide of hydrogen having two neutrons
Exe rc i ses
531
(k) mass number (A)
(Sec.18.2)
nuclear equation
(1)
(Sec. 18.2)
(m)
(n)
(o)
(p)
(q)
nuclear fission (Sec. 18.7)
nuclear fusion (Sec. 18.8)
nuclear reaction (Sec. 18.2)
nuclide (Sec. 18.2)
parent-daughter
nuclides (Sec. 18.3)
(r) positron (/3+) (Sec. 18.2)
(s) radioactive decay series
(Sec. 18.3)
radioactivity (Sec. 18.1)
(u) radionuclide (Sec. 18.5)
(v) transmutation (Sec. 18.6)
(w) tritium (Sec. 18.8)
(t)
Answers to odd-numbered Exercises are in Appendix I.
Natural Radioactivity (Sec. 18.1)
Which type of radiation is a helium nucleus and is deflected
toward the negative electrode as it passes between electrically charged plates?
2. Which type of radiation cannot penetrate human skin
and requires heavy paper or clothing as minimum protective shielding?
Which type of nuclear radiation is identical to an electron
and is deflected toward the positive electrode as it passes
between electrically charged plates?
4. Which type of radiation can penetrate about 1 cm of human
flesh and requires wood or aluminum as minimum protective shielding?
Which type of nuclear radiation is powerful light energy
that is not deflected as it passes between electrically
charged plates?
6. Which type of radiation can pass through the human
body and requires thick lead or concrete as minimum protective shielding?
<11111 Radon Test Kit The
earth releases radioactive
radon gas that may collect
beneath a home. Although
the gas is only present in
trace amounts, it may
accumulate in basements
and areas with minimal
ventilation and pose a
health hazard.
Nuclear Equations (Sec. 18.2)
What is the approximate mass for each of the following?
(a) alpha particle
(b) beta particle
(c) gamma ray
(d) positron
(e) neutron
(f) proton
8. What is the relative charge for each of the following?
(a) a
(c) y
(e) n°
(b) /3(d) 13+
(f) p+
Write an equation for each of the following natural radioactive decay processes:
(a) W-160 decays by alpha emission
(b) P-32 decays by beta emission
(c) Co-55 decays by positron emission
(d) Ti-44 decays by electron capture
10. Write an equation for each of the following natural radioactive decay processes:
(a) U-238 decays by alpha emission
(b) Al-28 decays by beta emission
(c) 0-15 decays by positron emission
(d) Fe-55 decays by electron capture
Identify X, an unknown radioactive nuclide, given the following information:
(a) Nuclide X decays by alpha emission to give 217Rn.
(b) Nuclide X decays by beta emission to give 43Ca.
(c) Nuclide X decays by positron emission to give 73Br.
(d) Nuclide X decays by electron capture to give 133Cs.
12. Identify X, an unknown radioactive nuclide, given the following information:
(a) Nuclide X decays by alpha emission to give 218 Ra.
(b) Nuclide X decays by beta emission to give 56Fe.
(c) Nuclide X decays by positron emission to give 19F.
(d) Nuclide X decays by electron capture to give 37Cl.
532
CHAPTER 18
NUCLEAR CHEMISTRY
Radioactive Decay Series (Sec. 18.3)
13. The uranium-238 decay series begins with the emission of
an alpha particle. The daughter product emits a beta particle to give which nuclide?
14. The uranium-235 decay series begins with the emission of
an alpha particle. The daughter product emits a beta particle to give which nuclide?
15. In the final step of the uranium-238 disintegration series,
the parent nuclide decays into lead-206 and an alpha particle. Identify the parent nuclide.
16. In the final step of the uranium-235 disintegration series,
the parent nuclide decays into lead-207 and a beta particle.
Identify the parent nuclide.
17. Supply each of the following emission particles in the 10-step
decay series for radioactive thorium-232:
22sA
89 c (c)
~228Th
2~§ Ra"'{d)
220Rn~)
86
90
2§~Po~
212pb~)
82
~
(h)
212
83
Bi
(i). .
.~J
18. Supply each of the following decaying nuclides in the 11-step
decay series for radioactive neptunium-237:
~(b)
~(c)
(d)~
a
/(f)~
20. Plutonium-241 decays in a series of 13 steps. In Step 11,
bismuth-213 emits a beta particle, followed by an alpha
particle, and ending with a beta particle. Identify the
radionuclide produced in Step 13 of the Pu-241 series.
Radioactive Half-Life (Sec. 18.4)
21. What percentage of U-238 radionuclides in a sample remain
after two half-lives?
22. What percentage of U-238 radionuclides in a sample remain
after three half-lives?
23. A nuclear reactor produces spent Pu-239 fuel rods that are
highly radioactive after they no longer support fission. If
15 half-lives are required for the nuclide to reach a safe level,
how long must the rods be stored (t 112 = 24,400 years)?
24. A nuclear fission reactor produces Sr-90 radioactive waste. If
20 half-lives are required for the nuclide to reach a safe level,
how long must the nuclear waste be stored (t 112 = 28.8 years)?
25. If the carbon-14 radioactivity of an ancient wooden artifact
is 6.25% that of a reference sample, what is the estimated
age of the artifact (t 112 = 5730 years)?
26. If the carbon-14 reading of a fossil bone is 60 dpm, and a
recent bone is 240 dpm, what is the estimated age of the fossil (t 1 ;2 = 5730 years)?
27. Sodium-24 in the form of NaCl is given as an injection to
measure the sodium electrolyte balance. If 80 mg of the
medical radionuclide is injected, how much Na-24 remains
after 60 hours (t 112 = 15 hours)?
28. If 160 mg of technetium-99 is administered for a medical
diagnosis, how much of the nuclide remains after 24 hours
<t112 = 6 hours)?
29. Small beads of iridium-192 are sealed in a plastic tube and
inserted through a needle into breast tumors. If an Ir-192 sample has an initial activity of 560 dpm, how much time is
required for the activity to drop to 35 dpm (t 112 = 74 days)?
30. If an iron-59 sample has an initial activity of 200 dpm, how
much time is required for the activity to drop to 25 dpm
(t112= 45 days)?
:n. The initial radioactivity of a cobalt-60 sample was 1200 dpm
and after 21.2 years the activity dropped to 75 dpm. What is
the half-life of the radionuclide?
32. If 2400 µg of hydrogen-3 decay to 600 µg after 24.8 years,
what is the half-life of this radionuclide that is used as a
chemical tracer?
Applications of Radionuclides (Sec. 18.5)
(e)
~(g)
(h)~
~(i)
(j)~
19. Plutonium-241 decays in a series of 13 steps, beginning
with the emission of a beta particle, followed by an alpha
particle, followed by another alpha particle. Identify the
radionuclide produced in Step 3 of the Pu-241 series.
33. What radionuclide technique can be used to estimate the
age of geological events up to a few billion years?
34. What radionuclide technique can be used to estimate the
age of fossils up to 50,000 years old?
35. What radionuclide can be used to sterilize male insects and ·
control pests?
36. What radionuclide can be used to irradiate food and
destroy microorganisms?
37. What y-emitting radionuclide is used to power pacemake
for heart patients?
38. What y-emitting radionuclide can be used to diagnose an
locate inactive lung tissue in the respiratory system?
39. What /3-emitting radionuclide can be used to measure the ,
activity of the thyroid gland?
i
EXERCISES
!O. What /3-emitting radionuclide can be used to diagnose ane-
mia by attaching to a hemoglobin molecule?
What y-emitting radionuclide can be used to diagnose and
locate brain tumors?
12. What y-emitting radionuclide can be used to treat
breast cancer?
How many neutrons are produced from the following fission reaction?
U
2 ~g
s;
+ An
---> 1 ~~
Ba + ~!, Kr + tin
60. How many neutrons are produced from the following fission reaction?
2 ~~
Bombarding Br-81 with gamma rays gives a radioactive
nuclide and a neutron. Identify the radionuclide.
'4. Bombarding Na-23 with a proton gives a radioactive
nuclide and a neutron. Identify the radionuclide.
Bombarding U-238 with a hydrogen-2 nucleus produces a
radioactive nuclide, a beta particle, and two neutrons.
Identify the radionuclide.
Bombarding Li-6 with a neutron produces a radioactive
nuclide and an alpha particle. Identify the radionuclide.
Firing a hydrogen-2 nucleus at a target nucleus gives 1-131
and a neutron. What is the target nuclide?
Firing a neutron at a target nucleus gives Mn-56 and an
alpha particle. What is the target nuclide?
Firing an accelerated particle at a boron-10 target nucleus produces N-14 and a gamma ray. What is the projectile particle?
Firing an accelerated particle at a Mg-26 target nucleus produces Mg-27 and a proton. What is the projectile particle?
Jn 1967, a Russian team smashed a neon nucleus into an
americium target and claimed it had synthesized a new element, X. Given the equation for the reaction, what nuclide
did the team create?
533
U
+ r~ n - - 1~1 Xe + j~ Sr + r\ n
How many neutrons are produced from the following fission reaction?
2 ~~
Pu
+ /1 n
------> 1 ~~
Cs + 1 ~8 Y +
i1
n
62. How many neutrons are produced from the following fis-
sion reaction?
2 0~
Pu + r\ n - - 1~~ La + ~* Rb + /1 n
What nuclide undergoes nuclear fission to give barium-143,
krypton-88, and three neutrons?
64. What nuclide undergoes nuclear fission to give xenon-142,
strontium-90, and two neutrons?
Am + TB Ne - - ~ X + 5 r\ n
In 1970, a group at the University of California at Berkeley
fired a nitrogen nucleus into a californium target and
.jaimed it had synthesized a new element, X. Given the
·~quation for the reaction, what nuclide did the group create?
2 ~~
Cf + 1 ~ N - - ~ X + 4 6n
in 1974, a team of Russian physicists smashed a chromium;4 nucleus into a lead-207 target. If a new element, X, and
me neutron were produced from the collision, what
-mclide did the team create?
5'! ·n 1976, a team of German physicists smashed a chromium'"i4 nucleus into a bismuth-209 target. If a new element, X,
md one neutron were produced from the collision, what
•.uclide did the team create?
a neutron causes a fission reaction that releases two neu' rnns, how many neutrons have been produced from the
. hird fission step? (Assume each step in the fission process
·~leases two neutrons.)
56.. :'a neutron causes a fission reaction that releases three neu··ons, how many neutrons have been produced from the
1ird fission step? (Assume each step in the fission process
"leases three neutrons.)
-he fission of uranium-235 produces 2.4 neutrons per
.ctcleus. Why is there a fractional value for the number of
·eutrons released?
58. Jhy must uranium ore be enriched in U-235 before it can
·~ used in the fuel rods of a nuclear reactor?
A. Nuclear Fission In a uranium-235 atomic bomb
explosion, the large uranium nucleus splits (fissions) into
two smaller fragments, and releases neutrons and energy.
The nuclear fusion of two deuterium nuclei gives a tritium
nucleus, a positron, and particle X Identify particle X.
66. The nuclear fusion of two helium-3 nuclei gives two protons and particle X. Identify particle X.
The nuclear fusion of a helium-3 nucleus and particle X
releases an alpha particle and a positron. Identify particle X.
68. The nuclear fusion of a lithium-7 nucleus and particle X
releases two alpha particles and a neutron. Identify
particle X.
The nuclear fusion of two identical nuclides produces
an alpha particle and a gamma ray. Identify the
fusion nuclide.
70. The nuclear fusion of two identical nuclides produces a deuterium nucleus and a positron. Identify the fusion nuclide.
534
CHAPTER 18
NUCLEAR CHEMISTRY
General Exercises
Tl. Plutonium-241 undergoes a 13-step decay series. If an
72.
73.
74.
75.
76.
77.
78.
alpha particle is emitted in the first step, what is the
daughter product?
Plutonium-241 undergoes a 13-step decay series. If an alpha
particle is emitted in the first step followed by a beta particle, what is the granddaughter product?
Nuclide X has a half-life of 23 s and decays by beta emission
to produce Xe-136 and a neutron. Write a nuclear equation
for the reaction.
Nuclide X has a half-life of 2.6 years and decays by electron
capture to produce Mn-55 and a gamma ray. Write a nuclear
equation for the reaction.
Crater Lake in Oregon was formed by volcanic explosion. If
a tree charred by the explosion gave an activity of -7.7 dpm
and the half-life of C-14 is 5730 years, what is the approximate age of Crater Lake?
Uranipm-lead dating of lunar rock samples gave a U-238 to
Pb-206 ratio of -1.0. If the half-life of U-238 is 4.5 billion
years, what is the approximate age of the lunar rocks?
A radionuclide ionizes the air in a smoke detector, which in
turn allows the flow of electricity. When smoke particles
enter the detector, they disrupt the electric current and set
off an alarm. What a-emitting radionuclide is used to ionize
the air in a smoke detector? (Hint: The radionuclide decays
into Np-237.)
A PET scan is a medical imaging technique for the circulatory system. First, a radionuclide is injected that decays
79.
80.
81.
82.
83.
84.
by positron emission. When the positron is emitted, it
strikes an electron, causing mutual annihilation and the
release of two gamma rays. Write an equation for the
annihilation reaction.
Element 99 was first synthesized by bombarding uranium238 with neutrons. The reaction yielded Es-253 and seven
beta particles. How many neutrons are necessary to balance
the equation?
Element 100 was first synthesized by bombarding uranium238 with neutrons. The reaction yielded Fm-255 and eight
beta particles. How many neutrons are necessary to balance
the equation?
In 1955, a single atom of a new element was synthesized
using the cyclotron at the University of California at
Berkeley. If Es-253 reacted with an alpha particle to release a
neutron, what new nuclide was produced?
In the Middle Ages, alchemists attempted to transmute
base metals into gold. Recently, platinum has been transmuted into gold by bombarding Pt-198 with a deuterium
nucleus to give a platinum nuclide and a proton. If
the platinum nuclide decays by beta emission, what
nuclide results?
The nuclear fusion of deuterium and tritium in a hydrogen
bomb releases an alpha particle, energy, and nuclide X.
Identify nuclide X.
The nuclear fission of lithium-6 in an atomic bomb
releases an alpha particle, energy, and nuclide X. Identify
nuclide X.
18 ch apte r se If-Te st Ao~·~
1. Which type of nuclear radiation is identical to an electron
and is deflected toward the positive electrode as it passes
between electrically charged plates? (Sec. 18.1)
(a) alpha
(b) beta
(c) gamma
(d) all of the above
(e) none of the above
2. What is the approximate mass and relative charge of
gamma radiation? (Sec. 18.2)
(a) 4 amu and +2
(b) 1 amu and +1
1 amu and 0
(d) 0 amu and 0
0 amu and-1
3. What is the name of the particle having the following notation:+~ e? (Sec. 18.2)
(a) electron
(b) neutron
(c) positron
(d) proton
(e) none of the above
4. What particle is emitted when a Ra-221 nucleus decays to
Rn-217? (Sec. 18.2)
(a) alpha
(b) beta
(c) neutron
(d) positron
(e) proton
(c)
(e)
to S•"'-'"" io Appoodid
5. In the final step of the uranium-235 decay series, the parent
nuclide decays to a lead-207 nuclide and a beta particle.
What is the parent nuclide? (Sec. 18.3)
(a) 2g~ Pb
(b) 2g~ Pb
(c) 2g~ Bi
(d) 2gi Tl
(e) none of the above
6. If an iron-59 sample has an initial activity of 160 dpm, how
much time is required for the activity to drop to 20 dpm
U1;2 = 45 days)? (Sec. 18.4)
(a) 45 days
(b) 90 days
(c) 135 days
(d) 180 days
(e) 210 days
7. What is the principle assumption for radiocarbon dating to
be reliable? (Sec. 18.5)
(a) The amount of nitrogen-14 in the atmosphere has
remained constant.
(b) The amount of carbon-14 in the atmosphere has
remained constant.