Physics for Scientists and Engineers, 6e
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Transcript of Physics for Scientists and Engineers, 6e
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Physics for Scientists and Engineers, 6e
Chapter 44 - Nuclear Structure
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Consider the following three nuclei: 12C, 13N, 14O. These nuclei have the same
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1. number of protons
2. number of neutrons
3. number of nucleons
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The value of N = A – Z is the same for all three nuclei.
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Consider the following three nuclei: 12N, 13N, 14N. These nuclei have the same
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1. number of protons
2. number of neutrons
3. number of nucleons
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The value of Z is the same for all three nuclei because they are all nuclei of nitrogen.
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Consider the following three nuclei: 14C, 14N, 14O. These nuclei have the same
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1 2 3 4 5
1. number of protons
2. number of neutrons
3. number of nucleons
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The value of A is the same for all three nuclei, as seen by the unchanging pre-superscript.
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On your birthday, you measure the activity of a sample of 210Bi, which has a half-life of 5.01 days. The activity you measure is 1.000 μCi. What is the activity of this sample on your next birthday?
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1. 1.000 μCi
2. 0
3. ~ 0.2 μCi
4. ~ 0.01 μCi
5. ~ 10–22 μCi
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A year of 365 days is equivalent to 365 d/5.01 d ≈ 73 half-lives. Thus, the activity will be reduced after one year to approximately (1/2)73 (1.000 μCi) ~ 10–22 μCi.
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Suppose you have a pure radioactive material with a half-life of T1/2. You begin with N0 undecayed
nuclei of the material at t = 0. At 1/2t = T1/2, how
many of the nuclei have decayed?
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1. 1/4N0
2. 1/2N0
3. 3/4N0
4. 0.707N0
5. 0.293N0
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The time we are interested in is half of a half-life. Thus, the number of remaining nuclei is (1/2)1/2N0 = N0 / √2 = 0.707N0. The number of
nuclei that have decayed is N0 – 0.707N0 =
0.293N0.
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Which of the following is the correct daughter nucleus associated with the alpha decay of ?
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1.
2.
3.
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In alpha decay, the atomic number decreases by two and the atomic mass number decreases by four.
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Which of the following is the correct daughter nucleus associated with the beta decay of ?
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1.
2.
3.
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In e– decay, the atomic number increases by one and the atomic mass number stays fixed. None of the choices is consistent with e+ decay, so we assume that the decay must be by e–.
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Which of the following do you expect not to vary substantially mong different isotopes of an element?
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1. atomic mass number
2. nuclear spin magnetic moment
3. chemical properties
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Isotopes of a given element correspond to nuclei with different numbers of neutrons. This results in different atomic mass numbers of the nucleus—and different magnetic moments, because the neutron, despite being uncharged, has a magnetic moment. The chemical behavior, however, is governed by the electrons. All isotopes of a given element have the same number of electrons and, therefore, the same chemical behavior.