GENERAL CHEMISTRY PRINCIPLES AND MODERN APPLICATIONS ELEVENTH EDITION

Nuclear Chemistry Slide 25 - 2 CONTENTS 25 -1 Radioactivity 25 -2 Naturally Occurring

Nuclear Chemistry Slide 25 - 3 CONTENTS 25 -9 Nuclear Fission 25 -10 Effect

25 -1 The Phenomenon of Radioactivity Alpha Particles, α Nuclei of He atoms, 24

Beta Particles, β Electrons originating from the nuclei of atoms in a nuclear decay

Positrons, β+ Simplest process is the decay of a free proton: 1 p 1

A colorized cloud chamber photograph. Slide 25 - 7 General Chemistry: Chapter 25 Copyright

Electron Capture Electron capture achieves the same effect as positron emission. 202 Ti 81

Gamma Rays, γ Gamma rays. Highly penetrating energetic photons. 234 U 92 230 Th‡

25 -2 Naturally Occurring Radioactive Isotopes 238 U 92 → 234 Th 90 +

FIGURE 25 -2 The natural radioactive decay series for 238 92 U (uranium series)

Radioactivity is common in heavy elements but relatively rare among naturally occurring lighter elements.

25 -3 Nuclear Reactions and Artificially Induced Radioactivity Rutherford 1919. 14 N 7 +

25 -4 Transuranium Elements 238 92 U + 01 n → → 239 93

Stanford Linear Accelerator Centre (SLAC 0 PEP-II collider) Slide 25 - 15 General Chemistry:

FIGURE 25 -3 The cyclotron Slide 25 - 16 General Chemistry: Chapter 25 Copyright

25 -5 Rate of Radioactive Decay The rate of disintegration of a radioactive material

Slide 25 - 18 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Radiocarbon Dating 14 7 N 14 6 C → + 01 n → 14

The Age of Earth 238 U 92 14 steps 206 Pb 82 + 8

Modern Radioactive Dating (Geochronology) N 0 = Slide 25 - 21 1 λ General

25 -6 Energetics of Nuclear Reactions E = mc 2 (25. 19) In chemical

FIGURE 25 -5 Nuclear binding energy in 24 He Slide 25 - 23 General

FIGURE 25 -6 Average binding energy per nucleon as a function of atomic number

25 -7 Nuclear Stability Shell Theory Slide 25 - 25 General Chemistry: Chapter 25

Slide 25 - 26 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

FIGURE 25 -7 Neutron-to-proton ratio and the stable nuclides up to Z=83 Slide 25

25 -8 Nuclear Fission 1934 Enrico Fermi. Search for transuranium elements U was bombarded

235 U 92 + 1 01 n fission fragments + neutrons + 3. 20×

Nuclear Reactors FIGURE 25 -8 Nuclear fission of 235 U with thermal neutrons 92

FIGURE 25 -9 Pressurised water nuclear reactor Slide 25 - 31 General Chemistry: Chapter

Breeder Reactors Fertile nuclides can produce fissile material. + 1 01 n → 238

Disadvantages of Breeder Reactors Liquid-metal-cooled fast breeder reactor (LMFBR). • Sodium becomes highly radioactive

25 -9 Nuclear Fusion produces the energy of the sun. Most promising process on

The plasma chamber of a fusion reactor of the magnetic confinement type (tokamak). Slide

25 -10 Effect of Radiation on Matter Ionizing radiation. Power described in terms of

FIGURE 25 -10 Some interactions of radiation with matter Slide 25 - 37 General

Radiation Detectors FIGURE 25 -11 A Geiger-Müller counter Slide 25 - 38 General Chemistry:

Effect of Ionizing Radiation on Living Matter Effect is the same as on other

Slide 25 - 40 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

25 -11 Applications of Radioisotopes Cancer Therapy In low doses, ionizing radiation induces cancer.

Radioactive Tracers Nuclear medicine provides methods for diagnosing life-threatening conditions Slide 25 - 42

Structures and Mechanisms 35 S 32 SO 2−(aq) + 3 H+(aq) H 2 O(l)

Analytical Chemistry Precipitate ions and weigh them to get a mass of material. Incorporate

Radiation Processing Strawberries that have been preserved by irradiation Slide 25 - 45 General

End of Chapter Slide 25 - 46 General Chemistry: Chapter 25 Copyright © 2017

Slides: 46

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GENERAL CHEMISTRY PRINCIPLES AND MODERN APPLICATIONS ELEVENTH EDITION PETRUCCI HERRING MADURA Nuclear Chemistry BISSONNETTE 25 PHILIP DUTTON UNIVERSITY OF WINDSOR DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY Slide 25 - 1 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Nuclear Chemistry Slide 25 - 2 CONTENTS 25 -1 Radioactivity 25 -2 Naturally Occurring Radioactive Isotopes 25 -3 Nuclear Reactions and Artificially Induced Radioactivity 25 -4 Transuranium Elements 25 -5 Rate of Radioactive Decay 25 -6 Energetics of Nuclear Reactions 25 -7 Nuclear Stability 25 -8 Nuclear Fission General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Nuclear Chemistry Slide 25 - 3 CONTENTS 25 -9 Nuclear Fission 25 -10 Effect of Radiation on Matter 25 -11 Applications of Radioisotopes General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

25 -1 The Phenomenon of Radioactivity Alpha Particles, α Nuclei of He atoms, 24 He 2+, the α particle is represented as 42 He Low penetrating power, stopped by a sheet of paper. 238 U 92 → 234 Th 90 + 24 He (25. 1) 1. The sum of the mass numbers must be the same on both sides. 2. The sum of the atomic numbers must be the same on both sides Slide 25 - 4 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Beta Particles, β Electrons originating from the nuclei of atoms in a nuclear decay process. Simplest process is the decay of a free neutron: 1 n 0 → 11 p +− 10β + ν 234 Th 90 Slide 25 - 5 → 234 Pa 91 + − 10β General Chemistry: Chapter 25 (25. 2) (25. 3) Copyright © 2017 Pearson Canada Inc.

Positrons, β+ Simplest process is the decay of a free proton: 1 p 1 → 01 n ++10β (25. 4) Commonly encountered in artificially produced radioactive nuclei of the lighter elements: 30 P 15 Slide 25 - 6 → 30 Si 14 + +10β General Chemistry: Chapter 25 (25. 5) Copyright © 2017 Pearson Canada Inc.

Electron Capture Electron capture achieves the same effect as positron emission. 202 Ti 81 Slide 25 - 8 + − 10β 202 Hg ‡ 80 General Chemistry: Chapter 25 202 Hg 80 + X-ray (25. 6) Copyright © 2017 Pearson Canada Inc.

Gamma Rays, γ Gamma rays. Highly penetrating energetic photons. 234 U 92 230 Th‡ 90 + 42 He (25. 7) + (25. 8) 234 Th 90 FIGURE 25 -1 Production of γ-rays Slide 25 - 9 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

25 -2 Naturally Occurring Radioactive Isotopes 238 U 92 → 234 Th 90 + 24 He 234 Th 90 → 234 Pa 91 + − 10β 234 Pa 91 → 234 U 92 +− 10β Daughter nuclides are new nuclides produced by radioactive decay. Slide 25 - 10 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Radioactivity is common in heavy elements but relatively rare among naturally occurring lighter elements. Naturally occurring 40 K decays by both β emission and e− capture. 40 20 Ca 40 K 19 Slide 25 - 12 + + 0 e − 1 General Chemistry: Chapter 25 0 − 1 β 40 Ar 18 Copyright © 2017 Pearson Canada Inc.

25 -3 Nuclear Reactions and Artificially Induced Radioactivity Rutherford 1919. 14 N 7 + 42 He 17 O 8 + 11 H (25. 9) + 10 n (25. 10) Iréne Joliot-Curie. 27 Al 13 + 42 He 30 15 P 30 P 15 30 14 Si + +10β Iréne Joliot-Curie (1897 -1956) Slide 25 - 13 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

25 -4 Transuranium Elements 238 92 U + 01 n → → 239 93 Np + 157 N → 260 105 U 239 92 U 249 98 Cf Slide 25 - 14 239 92 U General Chemistry: Chapter 25 + 0 + − 1 β + 4 01 n (25. 10) Copyright © 2017 Pearson Canada Inc.

25 -5 Rate of Radioactive Decay The rate of disintegration of a radioactive material – called the activity, A, or the decay rate – is directly proportional to the number of atoms. rate of decay Nt ln N 0 Slide 25 - 17 = −λt ∝N and rate of decay = A = λN (25. 12) General Chemistry: Chapter 25 ln(2) t½ = λ (25. 11) (25. 13) Copyright © 2017 Pearson Canada Inc.

Radiocarbon Dating 14 7 N 14 6 C → + 01 n → 14 7 N + 0 − 1 β + 11 H 14 6 C t½ = 5730 Years • Live organisms maintain 14 C/13 C at equilibrium. • Upon death, 14 C/13 C ratio changes due to decay. • Measure ratio and determine time since death. Slide 25 - 19 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

The Age of Earth 238 U 92 14 steps 206 Pb 82 + 8 24 He + 6− 10β A lunar rock that has been radiometrically dated to be about 4. 6 billion years old. Slide 25 - 20 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Modern Radioactive Dating (Geochronology) N 0 = Slide 25 - 21 1 λ General Chemistry: Chapter 25 N = N 0 e−λt (25. 14) N 0 = N + D (25. 15) 1 λ ln ln D N +1 Dt − D 0 N +1 Copyright © 2017 Pearson Canada Inc. (25. 16) (25. 17)

25 -6 Energetics of Nuclear Reactions E = mc 2 (25. 19) In chemical reactions ΔE is too small to notice m. In nuclear reactions ΔE is large enough to see m. 1 Me. V = 1. 6022× 10− 13 J (25. 20) If m = 1. 0 u then ΔE =1. 4924× 10− 10 J = 931. 5 Me. V Slide 25 - 22 General Chemistry: Chapter 25 (25. 22) Copyright © 2017 Pearson Canada Inc.

25 -8 Nuclear Fission 1934 Enrico Fermi. Search for transuranium elements U was bombarded with neutrons. β emission was observed. 1938 Otto Hahn, Lise Meitner, and Fritz Stassman. Z was not greater than 92. Ra, Ac, Th and Pa were found. The atom had been split. Slide 25 - 28 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

235 U 92 + 1 01 n fission fragments + neutrons + 3. 20× 10− 11 J Energy released is 8. 2× 107 k. J/g U. This is equivalent to the energy from burning 3 tons of coal. Slide 25 - 29 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Breeder Reactors Fertile nuclides can produce fissile material. + 1 01 n → 238 U 92 239 U 92 → 239 Np 93 + 0 − 1 β 239 Np 93 → 239 Pu 94 + 0 − 1 β 238 U 92 235 U 92 Slide 25 - 32 239 U 92 ≈ 100 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Disadvantages of Breeder Reactors Liquid-metal-cooled fast breeder reactor (LMFBR). • Sodium becomes highly radioactive in the reactor. • Heat and neutron production are high, so materials deteriorate more rapidly. • Radioactive waste and plutonium recovery. Plutonium is highly poisonous and has a long half life (24, 000 years). Slide 25 - 33 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

25 -9 Nuclear Fusion produces the energy of the sun. Most promising process on earth would be: 2 1 H + 13 H 4 2 He + 10 n + energy Plasma temperatures over 40, 000 K to initiate a self -sustaining reaction. Lithium is used to provide tritium and also act as the heat transfer material – handling problems. 7 3 Li + 1 0 n (fast) 3 4 He + 1 H 2 + 10 n (slow) Limitless power once reaction is self sustaining. Slide 25 - 34 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

25 -10 Effect of Radiation on Matter Ionizing radiation. Power described in terms of the number of ion pairs per cm of path through a material. Pα > P β > P γ Primary electrons ionized by the radioactive particle may have sufficient energy to produce secondary ionization. Slide 25 - 36 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Effect of Ionizing Radiation on Living Matter Effect is the same as on other forms of matter, ionization, excitation, and dissociation of molecules. Even small doses cause changes in cell chromosomes. Radiation Dosage 1 rad (radiation absorbed dose) = 0. 001 J/kg matter 1 rem (radiation equivalent for man) = rad×Q Q = relative biological effectiveness Slide 25 - 39 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

25 -11 Applications of Radioisotopes Cancer Therapy In low doses, ionizing radiation induces cancer. In high doses it destroys cells. Cancer cells are dividing quickly and are more susceptible to ionizing radiation than normal cells. The same is true of chemotherapeutic approaches. Slide 25 - 41 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Structures and Mechanisms 35 S 32 SO 2−(aq) + 3 H+(aq) H 2 O(l) + 32 SO 2(g) + 35 S(s) (25. 24) FIGURE 25 -12 Structure of thiosulfate ion, S 2 O 32− Slide 25 - 43 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.

Analytical Chemistry Precipitate ions and weigh them to get a mass of material. Incorporate radioactive ions in the precipitating mixture and measure the radioactivity. Neutron activation analysis. Induce radioactivity with neutron bombardment. Measure in trace quantities, down to ppb or less. Non-destructive and any state of matter can be probed. Slide 25 - 44 General Chemistry: Chapter 25 Copyright © 2017 Pearson Canada Inc.