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

Guiding Questions Is radiation dangerous? Is nuclear power a good choice? What is nuclear energy? Are nuclear energy and nuclear bombs both dangerous? More Specifically...: Give a brief history of radioactivity Define nuclear chemistry State that energy can be converted into matter List factors that determine stability of a nucleus Balance nuclear equations Distinguish between various forms of radiation in terms of penetration depth and energy Determine the half-life of a radioactive substance. Define nuclear fusion and fission Describe a chain reaction List applications of radioisotopes

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

© 2003 John Wiley and Sons Publishers Figure 4.1

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

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

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

Mass Defect Some of the mass can be converted into energy Shown by a very famous equation! E=mc2 Energy Mass Speed of light

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.

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

Products of Natural Radioactivity Mass Particle* Symbol Charge Number Identity Alpha 4 a 2+ 4 Helium nucleus 2 Beta 0 b 1- 0 Electron -1 Gamma 0 g 0 0 Proton of light *Sometimes a stream of any of these types of particles is called a ray, as in gamma ray,

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

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

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

b particle emission

particle emission Gamma rays are high-energy (short wavelength) electromagnetic radiation. They are denoted by the symbol. As you can see from the symbol, both the subscript and superscript are zero. 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.

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

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: 238U 4He + 234Th 92 2 90 214Pb 0 b + 214Bi 82 -1 83

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

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 = mc2 illustrates the energy found in even small amounts of matter

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: Energy is produced. More neutrons are given off.

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.

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

Fission produces a chain reaction

The fusion of hydrogen nuclei 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 hydrogen nuclei

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)

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

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

X-ray examination of luggage at a security station. © 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 g 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.

Images of human lungs obtained from a γ-ray scan. © 2003 John Wiley and Sons Publishers Images of human lungs obtained from a γ-ray scan. A compound containing radioactive technetium-99m was the source of the radiation. Courtesy CNRI/Phototake Images of human lungs obtained from a γ-ray scan.

A cancer patient receiving radiation therapy. © 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.

Cooling towers of a nuclear power plant. © 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

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.

Disposal of radioactive wastes by burial in a shallow pit. © 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.