Presentation on theme: "Nuclear Chemistry The study of the structure of atomic nuclei and the changes they undergo."— Presentation transcript:
1 Nuclear ChemistryThe study of the structure of atomic nuclei and the changes they undergo.
2 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 radioactivityDefine nuclear chemistryState that energy can be converted into matterList factors that determine stability of a nucleusBalance nuclear equationsDistinguish between various forms of radiation in terms of penetration depth and energyDetermine the half-life of a radioactive substance.Define nuclear fusion and fissionDescribe a chain reactionList applications of radioisotopes
3 Radioactive Decay Discovered by Antoine Henri Becquerel in 1896 He saw that photographic plates developed bright spots when exposed to uranium metals
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 Radioactive IsotopesStable 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.
7 Band of StabilityThe 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 ReactionsNuclear reactions are different from chemical reactionsChemical ReactionsMass is conserved (doesn’t change)Small energy changesNo changes in the nuclei; involve ONLY valance electronsNuclear ReactionsSmall changes in massHuge energy changesprotons, neutrons, electrons and gamma rays can be lost or gained
9 Mass Defect Some of the mass can be converted into energy Shown by a very famous equation!E=mc2EnergyMassSpeed of light
10 Types of RadiationThe effect of an electric field on three types of radiation is shown.Positively charged alpha particles are deflected toward the negatively charged plate.
12 Products of Natural Radioactivity MassParticle* Symbol Charge Number IdentityAlpha 4 a Helium nucleus2Beta 0 b Electron-1Gamma 0 g Proton of light*Sometimes a stream of any of these types of particles is called a ray, as in gamma ray,
18 particle emissionGamma 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.
19 Induced Nuclear Reactions Scientists can also force ( = induce) nuclear reactions by smashing nuclei with alpha, beta and gamma radiation to make the nuclei unstableor
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:238U 4He Th214Pb 0 b Bi
21 Balancing Nuclear Equations Complete the following nuclear equations:At Bi + ?Th b + ?-1Tl b + ?4He28583231Pa9190208Pb8281
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 energyAlbert Einstein’s equation E = mc2 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:Energy is produced.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) U + 1n U + ?(b) 9Be + 1H Li + ?(c) 9Be + 4He C + ?
27 The fusion of hydrogen nuclei Nuclear Fusionjoining 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
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) 1H C ?(b) 13N 13C + ?(c) 13C + 1H ?(d) 1H N ?(e) 15O 15N + ?(f) 15N + 1H 12C + ?Nuclear Fusion
30 Applications Medicine Agriculture Energy Chemotherapy Power pacemakers Diagnostic tracersAgricultureIrradiate foodPesticideEnergyFissionFusion
40 Challenges of Nuclear Power Disposal of waste products
41 Challenges of Nuclear Power Disposal of waste productsHazardous wastes produced by nuclear reactions are problematic.Some waste products, like fuel rods, can be re-usedSome products are very radioactive, and must be stored away from living things.Most of this waste is buried underground, or stored in concreteIt takes 20 half-lives (thousands of years) before the material is safe.