Nuclear Chemistry •The study of the structure of atomic nuclei and the changes they undergo. Radioactivity and Radioactive Decay Today’s Objective 1. Describe why certain nuclei are radioactive. 2. Write nuclear decay equations to depict the nuclear decay of radioisotopes. Isotopes - Atoms which possess the same atomic number, but different mass numbers. (Same number of protons, different number of neutrons) 1 2 3 1 1 1 Complete the Table Below Name Protons Neutrons Atomic Number Mass Number 6 8 6 14 K 19 22 19 41 Pb 82 124 82 206 Symbol Carbon-14 14 6 Potassium-41 41 19 Lead-206 206 82 C Radioactivity 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. Radioactive Isotopes 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. 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 Developed a formula to describe how some of the mass can be converted into energy. Shown by a very famous equation! E=mc2 Energy Mass When matters is turned into energy, large amounts of energy are released! Speed of light 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 = 12 + 1 13 = 13 Atomic Numbers: 4+2= 6+0 6 = 6 Finding the Missing Nucleus Th He ? 234 90 4 2 Mass Numbers 234 = 4 + ? ? = 230 Atomic Numbers 90 = 2 + ? ? = 88 230 88 Ra Finding the Missing Nucleus C e X 14 6 0 1 A Z Mass Numbers 14 = 0 + A A = 14 Atomic Numbers 6 = -1 + Z Z = 7 14 7 N Finding the Missing Nucleus 3 H Be X He 1 1 Mass Numbers Atomic Numbers 9 4 A Z (3 x 1) + 9 = A + 4 3 + 9 = A + 4 12 = A + 4 A = 8 (3 x 1) + 4 = Z + 2 3 + 4 = Z + 2 7 = Z + 2 Z = 5 4 2 8 5 B Examples of Transmutation Reactions C e N Th He Ra 234 90 4 2 14 6 230 88 0 1 14 7 3 H Be B He 1 1 9 4 8 5 4 2 These are all transmutation reactions because the elements on the left side are changed to produce a different element on the right side. Emissions from Radioisotopes Type of Particle Emitted Description Alpha A Helium Nucleus 4 2 Beta A Fast Moving Electron 0 1 Gamma Electromagnetic Radiation Neutron A neutron Symbol Mass Charge Why is it Emitted? He or 24 4 amu +2 Nucleus is too large. e or 1 amu 1840 -1 Too many neutrons 0 amu 0 Too much energy 1 0 0 1 0 0 1 ◦n Nucleus to heavy A radioisotope is a nucleus that is radioactive or unstable. © 2003 John Wiley and Sons Publishers Figure 4.4: The components of α rays, β rays, and γ rays. Radioactivity and Radioactive Decay Today’s Objective 1. Write nuclear decay equations to depict the nuclear decay of radioisotopes. Writing Nuclear Decay Equations Write the nuclear decay equation for the alpha decay of uranium-238. Start your decay equation by writing the symbol Write the symbol for the type for this nucleus and then follow it with an arrow. of decay. U He 238 92 4 2 234 90 Th Mass Number: 238 = 4 + ? ? = 234 Atomic Number: 92 = 2 + ? ? = 90 Writing Nuclear Decay Equations Write the nuclear decay equation for the beta decay of iodine-131. Start your decay equation by writing the symbol Write the symbol for the type for this nucleus and then follow it with an arrow. of decay. I e 131 53 0 1 131 54 Xe Mass Number: 131 = 0 + ? ? = 131 Atomic Number: 53 = -1 + ? ? = 54 Writing Nuclear Decay Equations Write the nuclear decay equation the emission of a gamma ray from carbon-14. Start your decay equation by writing the symbol Write the for the typean arrow. for this nucleus andsymbol then follow it with of decay. C C 14 6 0 0 14 6 Mass Number: 14 = 0 + ? ? = 14 Atomic Number: 6=0+? ?=6 Examples of Transmutation Reactions C e N Th He Ra 234 90 4 2 14 6 230 88 0 1 14 7 3 H Be B He 1 1 9 4 8 5 4 2 These are all transmutation reactions because the elements on the left side are changed to produce a different element on the right side. Decay Series for Uranium-238 This diagram shows the steps that an isotope of uranium takes to reach a stable isotope, lead-206. A Closer Look at the Decay Series Write a nuclear decay equation for what occurs to uranium-234 according to this decay series. U Th He 234 92 230 90 4 2 A Closer Look at the Decay Series Write a nuclear decay equation for what we occur to lead-210 according to this decay series. 210 82 Pb 210 83 Bi e 0 1 Writing Nuclear Decay Equations Write the nuclear decay equation for the alpha decay of uranium-238. Start your decay equation by writing the symbol Write the symbol for the type for this nucleus and then follow it with an arrow. of decay. U He 238 92 4 2 234 90 Th Mass Number: 238 = 4 + ? ? = 234 Atomic Number: 92 = 2 + ? ? = 90 Writing Nuclear Decay Equations Write the nuclear decay equation for the beta decay of iodine-131. Start your decay equation by writing the symbol Write the symbol for the type for this nucleus and then follow it with an arrow. of decay. I e 131 53 0 1 131 54 Xe Mass Number: 131 = 0 + ? ? = 131 Atomic Number: 53 = -1 + ? ? = 54 Writing Nuclear Decay Equations Write the nuclear decay equation the emission of a gamma ray from carbon-14. Start your decay equation by writing the symbol Write the for the typean arrow. for this nucleus andsymbol then follow it with of decay. C C 14 6 0 0 14 6 Mass Number: 14 = 0 + ? ? = 14 Atomic Number: 6=0+? ?=6 Two Types of Nuclear Reactions: Fission and Fusion Today’s Objective Compare and contrast fission and fusion. Type of Reaction Fission Fusion Fission versus Fusion Definition • Involves the splitting of a nucleus into two smaller nuclei • Often started when a nucleus is bombarded by a neutron • Involves two smaller nuclei joining together to create a larger nucleus Picture or Image Fission versus Fusion Fission Fusion Splitting of a Nucleus Releases smaller amounts of energy Controllable at Regular Temperatures Combining Nuclei Both Transmutation Reactions Releases larger amounts of energy Generally Requires Very High Temperatures Produces smaller quantities More Efficient of nuclear waste than Coal or Oil Examples include the Examples include sun, stars, and the nuclear power plants hydrogen bomb and the atom bomb Produces larger quantities of nuclear waste A transmutation reaction is a nuclear reaction that produces a new or different atom than was originally present. Fission produces a chain reaction 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) Radiation Exposure and Half-Life 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 Protecting Ourselves from Radioactive Particles © 2003 John Wiley and Sons Publishers Figure 4.2: The penetrating power of radiation. Current Nuclear Reactors Current Nuclear Reactors Inside a Nuclear Reactor Applications Medicine Chemotherapy Power pacemakers Diagnostic tracers Agriculture Irradiate food Pesticide Energy Fission Fusion © 2003 John Wiley and Sons Publishers Courtesy Robert Maass/Corbis Images X-ray examination of luggage at a security station. Food Irradiation •Food can be irradiated with rays from 60Co or 137Cs. •Irradiated milk has a shelf life of 3 mo. without refrigeration. •USDA has approved irradiation of meats and eggs. © 2003 John Wiley and Sons Publishers Courtesy Custom Medical Stock Photo An image of a thyroid gland obtained through the use of radioactive iodine. © 2003 John Wiley and Sons Publishers Courtesy CNRI/Phototake Images of human lungs obtained from a γ-ray scan. © 2003 John Wiley and Sons Publishers Courtesy Kelley Culpepper/Transparencies, Inc. A cancer patient receiving radiation therapy. © 2003 John Wiley and Sons Publishers Courtesy Scott Camazine/Photo Researchers The world’s first atomic explosion, July 16, 1945 at Alamogordo, New Mexico. © 2003 John Wiley and Sons Publishers Courtesy Shigeo Hayashi Remains of a building after the explosion of the uranium bomb at Hiroshima, August 6, 1945. © 2003 John Wiley and Sons Publishers Courtesy David Bartruff/Corbis Images Cooling towers of a nuclear power plant. © 2003 John Wiley and Sons Publishers Courtesy Sipa Press The nuclear power plant at Chernobyl, after the accident of April 16, 1986. Challenges of Nuclear Power »Disposal of waste products 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. © 2003 John Wiley and Sons Publishers Courtesy Yucca Mountain Project 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 Matthew Neal McVay/Stone/Getty Images Disposal of radioactive wastes by burial in a shallow pit. © 2003 John Wiley and Sons Publishers Courtesy AP/Wide World Photos Albert Einstein, he discovered the equation that relates mass and energy.