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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 Today’s Objective 1. Describe why certain nuclei are radioactive. 2. Write nuclear decay equations to depict the nuclear decay of radioisotopes. Radioactivity and Radioactive Decay

3 Isotopes - Atoms which possess the same atomic number, but different mass numbers. (Same number of protons, different number of neutrons)

4 NameSymbolProtonsNeutrons Atomic Number Mass Number Carbon Potassium Lead Complete the Table Below

5 What is radioactivity? Radioactivity occurs when an unstable nucleus spontaneously emits fragments of the nucleus and/or energy. Unstable Nucleus = Radioactive Why are only some isotopes radioactive? The ratio of protons to neutrons in the nucleus determines whether or not a nucleus is radioactive. Radioactivity

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 Developed a formula to describe how some of the mass can be converted into energy. Developed a formula to describe how some of the mass can be converted into energy. Shown by a very famous equation! Shown by a very famous equation! E=mc 2 E=mc 2 When matters is turned into energy, large amounts of energy are released! When matters is turned into energy, large amounts of energy are released! EnergyMass Speed of light

9 Depicting Nuclear Reaction For nuclear reactions, the sum of the mass numbers (top numbers) and the sum of the atomic numbers (bottom number) must be the same on both sides. Mass Numbers:9 + 4 = = 13 Atomic Numbers:4 + 2 = = 6

10 Finding the Missing Nucleus Mass Numbers 234 = 4 + ? ? = 230 Atomic Numbers 90 = 2 + ? ? = 88

11 Finding the Missing Nucleus Mass Numbers 14 = 0 + A A = 14 Atomic Numbers 6 = -1 + Z Z = 7

12 Finding the Missing Nucleus Mass Numbers (3 x 1) + 9 = A = A = A + 4 A = 8 Atomic Numbers (3 x 1) + 4 = Z = Z = Z + 2 Z = 5

13 Examples of Transmutation Reactions These are all transmutation reactions because the elements on the left side are changed to produce a different element on the right side.

14 Emissions from Radioisotopes Type of Particle Emitted DescriptionSymbolMassCharge Why is it Emitted? Alpha A Helium Nucleus 4 amu+2 Nucleus is too large. Beta A Fast Moving Electron Too many neutrons Gamma Electromagnetic Radiation 0 amu0 Too much energy NeutronA neutron 1◦1◦ 10Nucleus to heavy A radioisotope is a nucleus that is radioactive or unstable. n

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

16 Today’s Objective 1. Write nuclear decay equations to depict the nuclear decay of radioisotopes. Radioactivity and Radioactive Decay

17 Writing Nuclear Decay Equations Write the nuclear decay equation for the alpha decay of uranium-238. Start your decay equation by writing the symbol for this nucleus and then follow it with an arrow. Write the symbol for the type of decay. Mass Number:238 = 4 + ?? = 234 Atomic Number:92 = 2 + ?? = 90

18 Write the nuclear decay equation for the beta decay of iodine-131. Mass Number:131 = 0 + ?? = 131 Atomic Number:53 = -1 + ?? = 54 Writing Nuclear Decay Equations Start your decay equation by writing the symbol for this nucleus and then follow it with an arrow. Write the symbol for the type of decay.

19 Write the nuclear decay equation the emission of a gamma ray from carbon-14. Mass Number:14 = 0 + ?? = 14 Atomic Number:6 = 0 + ?? = 6 Writing Nuclear Decay Equations Start your decay equation by writing the symbol for this nucleus and then follow it with an arrow. Write the symbol for the type of decay.

20 Examples of Transmutation Reactions These are all transmutation reactions because the elements on the left side are changed to produce a different element on the right side.

21 Decay Series for Uranium-238 This diagram shows the steps that an isotope of uranium takes to reach a stable isotope, lead-206.

22 A Closer Look at the Decay Series Write a nuclear decay equation for what occurs to uranium-234 according to this decay series.

23 A Closer Look at the Decay Series Write a nuclear decay equation for what we occur to lead-210 according to this decay series.

24 Writing Nuclear Decay Equations Write the nuclear decay equation for the alpha decay of uranium-238. Start your decay equation by writing the symbol for this nucleus and then follow it with an arrow. Write the symbol for the type of decay. Mass Number:238 = 4 + ?? = 234 Atomic Number:92 = 2 + ?? = 90

25 Write the nuclear decay equation for the beta decay of iodine-131. Mass Number:131 = 0 + ?? = 131 Atomic Number:53 = -1 + ?? = 54 Writing Nuclear Decay Equations Start your decay equation by writing the symbol for this nucleus and then follow it with an arrow. Write the symbol for the type of decay.

26 Write the nuclear decay equation the emission of a gamma ray from carbon-14. Mass Number:14 = 0 + ?? = 14 Atomic Number:6 = 0 + ?? = 6 Writing Nuclear Decay Equations Start your decay equation by writing the symbol for this nucleus and then follow it with an arrow. Write the symbol for the type of decay.

27 Today’s Objective Compare and contrast fission and fusion. Two Types of Nuclear Reactions: Fission and Fusion

28 Fission versus Fusion Type of Reaction DefinitionPicture or Image Fission Involves the splitting of a nucleus into two smaller nuclei Often started when a nucleus is bombarded by a neutron Fusion Involves two smaller nuclei joining together to create a larger nucleus

29 Fission versus Fusion Fission Fusion Both Transmutation Reactions A transmutation reaction is a nuclear reaction that produces a new or different atom than was originally present. Splitting of a Nucleus Combining Nuclei Releases smaller amounts of energy Releases larger amounts of energy Controllable at Regular Temperatures Generally Requires Very High Temperatures Examples include nuclear power plants and the atom bomb Examples include the sun, stars, and the hydrogen bomb Produces larger quantities of nuclear waste Produces smaller quantities of nuclear waste More Efficient than Coal or Oil

30 Fission produces a chain reaction

31 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)

32 Today’s Objective Discuss how we protect ourselves from radiation and use nuclear chemistry. Determine the meaning of a half-life. Current uses of Nuclear reactions Radiation Exposure and Half-Life

33 Figure 4.2: The penetrating power of radiation. © 2003 John Wiley and Sons Publishers Protecting Ourselves from Radioactive Particles

34 Current Nuclear Reactors

35

36 Inside a Nuclear Reactor

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

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

39 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.

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

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

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

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

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

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

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

47 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

48 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

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

50 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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