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Nuclear Chemistry The study of the structure of atomic nuclei and the changes they undergo.

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Presentation on theme: "Nuclear Chemistry The study of the structure of atomic nuclei and the changes they undergo."— Presentation transcript:

1 Nuclear Chemistry The study of the structure of atomic nuclei and the changes they undergo.

2 Is radiation dangerous? Is nuclear power a good choice? What is nuclear energy? Are nuclear energy and nuclear bombs both dangerous? Guiding Questions

3 Radioactive Decay Discovered by Antoine Henri Becquerel in 1896 – He saw that photographic plates developed bright spots when exposed to uranium metals

4 Figure 4.1 © 2003 John Wiley and Sons Publishers

5 As you may recall, isotopes are atoms of the same element that have different numbers of neutrons. Isotopes of atoms with unstable nuclei are called radioisotopes

6 Stable Isotopes -Atoms that do not release protons or neutrons from the nucleus and ARE NOT RADIOACTIVE. Unstable Isotopes - Atoms that spontaneously release protons and neutrons from its nucleus. These isotopes ARE RADIOACTIVE. Radioactive Isotopes

7 Band of Stability The region on a graph which indicates all stable nuclei when the number of neutrons are compared to the number of protons for all stable nuclei

8 Nuclear Reactions Nuclear reactions are different from chemical reactions Chemical Reactions Mass is conserved (doesn’t change) Small energy changes No changes in the nuclei; involve ONLY valance electrons Nuclear Reactions Small changes in mass Huge energy changes protons, neutrons, electrons and gamma rays can be lost or gained

9 Mass Defect Some of the mass can be converted into energy Some of the mass can be converted into energy Shown by a very famous equation! Shown by a very famous equation! E=mc 2 EnergyMass Speed of light

10 Types of Radiation The effect of an electric field on three types of radiation is shown. Positively charged alpha particles are deflected toward the negatively charged plate.

11 Figure 4.2: The penetrating power of radiation. © 2003 John Wiley and Sons Publishers

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13 Figure 4.4: The components of α rays, β rays, and γ rays. © 2003 John Wiley and Sons Publishers

14 Types of radioactive decay alpha particle emission – loss of a helium nucleus.

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16 Beta decay, Nuclear changes that accompany the emission of a beta particle. Types of radioactive decay

17  particle emission

18 As you can see from the symbol, both the subscript and superscript are zero. Gamma rays are high-energy (short wavelength) electromagnetic radiation. They are denoted by the symbol. particle emission Thus, the emission of gamma rays does not change the atomic number or mass number of a nucleus. Gamma rays almost always accompany alpha and beta radiation, as they account for most of the energy loss that occurs as a nucleus decays.

19 Induced Nuclear Reactions Scientists can also force ( = induce) nuclear reactions by smashing nuclei with alpha, beta and gamma radiation to make the nuclei unstable or

20 BALANCING NUCLEAR EQUATIONS 1.The sums of mass numbers (left superscripts) on each side must be equal. 2.The sums of atomic numbers or nuclear charges (left subscripts) on each side of the equation must be equal. Examples: 238 U 4 He + 234 Th 922 90 214 Pb 0  214 Bi 82-1 83

21 Balancing Nuclear Equations Complete the following nuclear equations: 1. 217 At 213 Bi + ? 2. 231 Th 0  + ? 3. 208 Tl 0  + ? 85 83 4 He 2 90 231 Pa 91 208 Pb 82 81

22 Nuclear Reactions Two types: – Fission = the splitting of nuclei – Fusion = the joining of nuclei (they fuse together) Both reactions involve extremely large amounts of energy Albert Einstein’s equation E = mc 2 illustrates the energy found in even small amounts of matter

23 Nuclear Fission: Is the splitting of one heavy nucleus into two or more smaller nuclei, as well as some sub-atomic particles and energy. A heavy nucleus is usually unstable, due to many positive protons pushing apart. When fission occurs: 1.Energy is produced. 2.More neutrons are given off.

24 Nuclear Fission Neutrons are used to make nuclei unstable – It is much easier to crash a neutral neutron than a positive proton into a nucleus to release energy.

25 Nuclear Fission Complete the following nuclear equations: (a) 238 U + 1 n 239 U + ? (b) 9 Be + 1 H 6 Li + ? (c) 9 Be + 4 He 12 C + ?

26 Fission produces a chain reaction

27 Nuclear Fusion joining of two light nuclei into one heavier nucleus. – In the core of the Sun, two hydrogen nuclei join under tremendous heat and pressure to form a helium nucleus. – When the helium atom is formed, huge amounts of energy are released. The fusion of hydroge n nuclei

28 Scientists cannot yet find a safe, and manageable method to harness the energy of nuclear fusion. – “cold fusion” would occur at temperatures and pressures that could be controlled (but we haven’t figured out how to get it to happen)

29 Complete the following nuclear equations, thought to be the source of the energy of some stars. (a) 1 H + 12 C? (b) 13 N 13 C + ? (c) 13 C + 1 H? (d) 1 H + 14 N? (e) 15 O 15 N + ? (f) 15 N + 1 H 12 C + ? Nuclear Fusion

30 Applications Medicine – Chemotherapy – Power pacemakers – Diagnostic tracers Agriculture – Irradiate food – Pesticide Energy – Fission – Fusion

31 X-ray examination of luggage at a security station. © 2003 John Wiley and Sons Publishers Courtesy Robert Maass/Corbis Images

32 Food Irradiation Food can be irradiated with  rays from 60 Co or 137 Cs.Food can be irradiated with  rays from 60 Co or 137 Cs. Irradiated milk has a shelf life of 3 mo. without refrigeration.Irradiated milk has a shelf life of 3 mo. without refrigeration. USDA has approved irradiation of meats and eggs.USDA has approved irradiation of meats and eggs.

33 An image of a thyroid gland obtained through the use of radioactive iodine. © 2003 John Wiley and Sons Publishers Courtesy Custom Medical Stock Photo

34 Images of human lungs obtained from a γ-ray scan. © 2003 John Wiley and Sons Publishers Courtesy CNRI/Phototake

35 A cancer patient receiving radiation therapy. © 2003 John Wiley and Sons Publishers Courtesy Kelley Culpepper/Transparencies, Inc.

36 The world’s first atomic explosion, July 16, 1945 at Alamogordo, New Mexico. © 2003 John Wiley and Sons Publishers Courtesy Scott Camazine/Photo Researchers

37 Remains of a building after the explosion of the uranium bomb at Hiroshima, August 6, 1945. © 2003 John Wiley and Sons Publishers Courtesy Shigeo Hayashi

38 Cooling towers of a nuclear power plant. © 2003 John Wiley and Sons Publishers Courtesy David Bartruff/Corbis Images

39 The nuclear power plant at Chernobyl, after the accident of April 16, 1986. © 2003 John Wiley and Sons Publishers Courtesy Sipa Press

40 Challenges of Nuclear Power Disposal of waste products

41 Hazardous wastes produced by nuclear reactions are problematic. – Some waste products, like fuel rods, can be re-used – Some products are very radioactive, and must be stored away from living things. Most of this waste is buried underground, or stored in concrete It takes 20 half-lives (thousands of years) before the material is safe. Challenges of Nuclear Power » Disposal of waste products

42 Construction of a tunnel that will be used for burial of radioactive wastes deep within Yucca Mountain, Nevada. © 2003 John Wiley and Sons Publishers Courtesy Yucca Mountain Project

43 Disposal of radioactive wastes by burial in a shallow pit. © 2003 John Wiley and Sons Publishers Courtesy Matthew Neal McVay/Stone/Getty Images

44 Albert Einstein, he discovered the equation that relates mass and energy. © 2003 John Wiley and Sons Publishers Courtesy AP/Wide World Photos


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