zumdahl_chemprin_6e_csm_ch20

zumdahl_chemprin_6e_csm_ch20 - CHAPTER 20 THE NUCLEUS: A...

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756 CHAPTER 20 THE NUCLEUS: A CHEMIST'S VIEW Radioactive Decay and Nuclear Transformations 1. a. Thermodynamic stability: the potential energy of a particular nucleus compared to the sum of the potential energies of its component protons and neutrons. b. Kinetic stability: the probability that a nucleus will undergo decomposition to form a different nucleus. c. Radioactive decay: a spontaneous decomposition of a nucleus to form a different nucleus. d. Beta-particle production: a decay process for radioactive nuclides where an electron is produced; the mass number remains constant and the atomic number changes. e. Alpha-particle production: a common mode of decay for heavy radioactive nuclides where a helium nucleus is produced, causing the atomic number and the mass number to change. f. Positron production: a mode of nuclear decay in which a particle is formed having the same mass as an electron but opposite in charge. g. Electron capture: a process in which one of the inner-orbital electrons in an atom is captured by the nucleus. h. Gamma-ray emissions; the production of high-energy photons (gamma rays) that fre- quently accompany nuclear decays and particle reactions. 2. Beta-particle production has the net effect of turning a neutron into a proton. Radioactive nuclei having too many neutrons typically undergo beta-particle decay. Positron production has the net effect of turning a proton into a neutron. Nuclei having too many protons typically undergo positron decay. 3. All nuclear reactions must be charge-balanced and mass-balanced. To charge-balance, balance the sum of the atomic numbers on each side of the reaction, and to mass-balance, balance the sum of the mass numbers on each side of the reaction. a. V e Cr 51 23 0 1 51 24 + b . X e e I 131 54 0 1 131 53 + c. S e P 32 16 0 1 32 15 + d . T h He U 131 90 4 2 235 92 +
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CHAPTER 20 THE NUCLEUS: A CHEMIST'S VIEW 757 4. a. e Ge Ga 0 1 73 32 73 31 + b . H e Os Pt 4 2 188 76 192 78 + c. e Pb Bi 0 1 205 82 205 83 + + d . A m e Cm 241 95 0 1 241 96 + 5. a. Zn e Ga 68 30 0 1 68 31 + b. Ni e Cu 62 28 0 1 62 29 + + c. At He Fr 208 85 4 2 212 87 + d . T e e Sb 129 52 0 1 129 51 + 6. a. Np He Am 237 93 4 2 241 95 + b. . Bi is product final the ; Bi e 4 He 8 Am 209 83 209 83 0 1 4 2 241 95 + + c. α Ra α Th β U α Pa α Np Am 225 88 229 90 233 92 233 91 237 93 241 95 + + + + + + β Ac α Fr α At α Bi β Po 225 89 221 87 217 85 213 83 213 84 + + + + + β Bi α Pb 209 83 209 82 + + The intermediate radionuclides are: Pb and , Po , Bi , At , Fr , Ac , Ra , Th , U , Pa , Np 209 82 213 84 213 83 217 85 221 87 225 89 225 88 229 90 233 92 233 91 237 93 7. ; e ? He ? Pb Bk 0 1 4 2 207 82 247 97 + + The change in mass number (247 - 207 = 40) is due ex- exclusively to the alpha particles. A change in mass number of 40 requires 10 He 4 2 particles to be produced. The atomic number only changes by 97 82 = 15. The 10 alpha particles change the atomic number by 20, so e 5 0 1 (five beta particles) are produced in the decay series of 247 Bk to 207 Pb.
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zumdahl_chemprin_6e_csm_ch20 - CHAPTER 20 THE NUCLEUS: A...

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