Chapter 19: The Nucleus: A Chemist’s View
1. Identify the missing particle in the following equation:
U → He + ?
A)
Pu
B)
Th
C)
Th
D)
U
E)
none of these
2. The ratio of the atomic radius to the nuclear radius is approximately:
A)
10–5
B)
105
C)
102
D)
1015
E)
10–15
3. An unstable isotope of rhenium, 191Re, has a half-life of 9.8 minutes and is a beta producer.
What is the other product of the reaction?
A)
191Os
B)
191W
C)
192Pt
D)
190W
E)
190Os
4. The nuclide Th is radioactive. When one of these atoms decays, a series of and –
particle emissions occurs, taking the atom through many transformations to end up as an
atom of Pb. How many particles are emitted in converting Th into Pb?
A)
6
B)
8
C)
2
D)
214
E)
4
5. It is desired to determine the concentration of arsenic in a lake sediment sample by means of
neutron activation analysis. The nuclide captures a neutron to form , which in
turn undergoes decay. The daughter nuclide produces the characteristic rays used for the
analysis. What is the daughter nuclide?
A)
Se
B)
Ge
C)
Ga
D)
Se
E)
Se
6. Which of the following is a product of decay of U?
A)
Th
B)
Np
C)
Pa
D)
U
E)
Pu
7. Electron capture transforms K into what nuclide?
A)
Ca
B)
Ar
C)
He
D)
K–
E)
Ca
8. Which of the following processes decreases the atomic number by one?
A)
gamma-ray production
B)
electron capture
C)
beta-particle production
D)
positron production
E)
at least two of the above processes
9. If Pb undergoes a beta decay and the product of this decay undergoes another beta decay,
which nuclide is produced?
A)
Bi
B)
Pb
C)
Po
D)
Bi
E)
Pb
10. Electron capture transforms Be into what nuclide?
A)
Li
B)
B
C)
Li
D)
B
E)
C
11. A radioactive isotope of vanadium, V, decays by producing a particle and gamma ray.
The nuclide formed has the atomic number:
A)
22
B)
21
C)
23
D)
24
E)
none of these
12. The nuclide Tl is the daughter nuclide resulting from the decay of what parent nuclide?
A)
Pb
B)
Au
C)
Hg
D)
Bi
E)
He
13. The nuclide N is unstable. What type of radioactive decay would be expected?
A)
e
B)
e
C)
D)
E)
n
14. Nuclides with too many neutrons to be in the band of stability are most likely to decay by
what mode?
A)
alpha emission
B)
fission
C)
positron production
D)
electron capture
E)
beta emission
15. The most likely decay mode (or modes) of the unstable nuclide C would be:
A)
positron production
B)
-particle production
C)
electron capture
D)
-particle production
E)
either positron production or electron capture, or both.
16. When Np undergoes – emission, the products are:
A)
U + e–
B)
Pu + e–
C)
U + e–
D)
Pa + He
E)
Np + e–
17. Which reaction will produce an isotope of the parent nuclide?
A)
Po → He + ?
B)
Br → n + ?
C)
Ac → e– + ?
D)
N → e– + ?
E)
As + e– → ?
18. What is the most likely decay for the Fe-53 nucleus?
A)
decay
B)
positron emission
C)
decay
D)
-ray emission
E)
two of these
19. What is the most likely decay for the Fe-59 nucleus?
A)
decay
B)
positron emission
C)
decay
D)
-ray emission
E)
two of these
The U-238 nucleus decays to form Pb-206 by and decays.
20. Calculate the number of decays.
A)
2
B)
4
C)
6
D)
8
E)
none of these
21. Calculate the number of decays.
A)
2
B)
4
C)
6
D)
8
E)
none of these
22. Which types of processes are likely when the neutron-to-proton ratio in a nucleus is too
low?
I.
decay
II.
decay
III.
positron production
electron capture
A)
I, II
B)
II, III
C)
III, IV
D)
II, III, IV
E)
II, IV
23. The so-called “magic numbers” of protons and neutrons produce special chemical stability.
24. As atomic mass increases, the proton/neutron ratio of stable nuclides decreases.
25. The rate constant for the beta decay of thorium-234 is 2.882 10–2 / day. What is the half-
life of this nuclide?
A)
48.09 days
B)
1.218 days
C)
0.693 days
D)
24.05 days
E)
96.18 days
26. Consider a certain type of nucleus that has a rate constant of 2.95 10–2 min–1. Calculate the
time required for the sample to decay to one-fourth of its initial value.
A)
2.95 min
B)
0.0590 min
C)
23.5 min
D)
29.4 min
E)
47.0 min
27. Consider a certain type of nucleus that has a half-life of 32 min. Calculate the percent of
original sample of nuclides remaining after 2.5 hours have passed.
A)
96%
B)
40%
C)
6.9%
D)
3.9%
E)
3.2%
28. Consider a certain type of nucleus that has a half-life of 32 min. Calculate the time required
for 52% of the nuclides to decompose.
A)
30 min
B)
21 min
C)
49 min
D)
42 min
E)
34 min
29. The number of a certain radioactive nuclide present in a sample decays from 160. to 20. in
39 minutes. What is the half-life of this radioactive species?
A)
8 minutes
B)
13 minutes
C)
18 minutes
D)
23 minutes
E)
28 minutes
30. The half-life of is 28 years. How long will it take for a given sample of to be 89%
decomposed?
A)
9.0 half-lives
B)
5 years
C)
89 years
D)
2.2 years
E)
none of these
31. The number of half-lives needed for a radioactive element to decay to about 6% of its
original activity is (choose nearest number):
A)
2
B)
3
C)
4
D)
5
E)
6
32. The Br-82 nucleus has a half-life of about 1.0 103 minutes. If you wanted 2.2 g of Br-82
and the delivery time was three days, about how much NaBr should you order (assuming all
of the Br in the NaBr was Br-82)?
A)
2.2 g
B)
4.4 g
C)
4.0 g
D)
57 g
E)
7.8 g
33. A radioactive sample has an initial activity of 2.00 106 cpm (counts per minute), and after
4.0 days, its activity is 9.0 105 cpm. What is its activity after 29 days?
A)
8.7 cpm
B)
6.1 103 cpm
C)
3.3 102 cpm
D)
1.5 10–9 cpm
E)
none of these
A certain radioactive sample contains 2.4 103 nuclides at a certain time (t = 0); 3.0 h later
the sample contains 6.0 102 nuclides.
34. For this sample the ratio of the decay rates at t = 0 to t = 3.0 h is:
A)
1.0
B)
8.0
C)
4.0
D)
16
E)
none of these
35. The value of the rate constant for this process is:
A)
2.2 h–1
B)
4.6 10–1 h–1
C)
1.6 h–1
D)
3.0 h–1
E)
none of these
36. The half-life of is 28.1 years. How long will it take a 10.0-g sample of to
decompose to 0.23 g?
A)
102 years
B)
306 years
C)
153 years
D)
229 years
E)
none of these
37. The rate constant for the decay of is 4.234 10–3 / day. What is the half-life of
A)
81.84 days
B)
163.7 days
C)
327.4 days
D)
409.2 days
E)
none of these
38. A radioactive element has a half-life of 1.6 hours. How many hours will it take for the
number of atoms present to decay to one-sixteenth of the initial value?
A)
26
B)
13
C)
6.4
D)
0.15
E)
16
39. The half-life of a sample has been defined as the time it takes for half of a sample to decay.
The fifth-life can be defined as the time it takes for one-fifth of a sample to decay. Given
these definitions, calculate the fifth-life of a sample that has a half-life of 26 years.
A)
8.4 years
B)
60 years
C)
17 years
D)
29 years
E)
42 years
40. The Cs-131 nuclide has a half-life of 30. years. After 144 years, about 3.0 grams remain.
The original mass of the Cs-131 sample is closest to
A)
167 g
B)
42 g
C)
84 g
D)
292 g
E)
100 g
41. The I-131 nuclide has a half-life of 8.0 days. If you originally have a 1.8-kg sample, after
1.4 months you will have approximately
A)
95 g
B)
62 g
C)
71 g
D)
47 g
E)
less than 1 g
42. Use the following table to assist in answering the question below.
Nuclide
Half-Life
Uranium-238
4.51 109 years
Uranium-234
2.48 105 years
Thorium-230
8.0 104 years
Radium-226
1.62 103 years
Lead-210
20.4 years
The rate constant for the decay of unstable nuclide X by alpha-particle emission is
4.21 10–13 / day. What is the identity of X?
A)
Radium-226
B)
Thorium-230
C)
Uranium-234
D)
Uranium-238
E)
Lead-210
43. The half-life for electron capture for is 1.30 109 years. What percent of the original
remains after 3.24 109 years?
A)
82.2%
B)
17.8%
C)
75.7%
D)
24.3%
E)
44.4%
44. Identify the missing particle in the following nuclear equation:
Am + He → __________ + 2 n
A)
Bk
B)
Bk
C)
Bk
D)
Bk
E)
Bk
45. In the following nuclear equation, identify the missing product:
Ca + → __________ + H
A)
Ti
B)
Sc