Nuclear Chemistry PDF

Nuclear Chemistry Nuclear Energy - Also called atomic energy - Energy that is released in significant amounts in processes that affect atomic nuclei (dense cores of atoms) - It is dis nct from the energy of other atomic phenomena such as ordinary chemical reac on, which...

Nuclear Chemistry Nuclear Energy - Also called atomic energy - Energy that is released in significant amounts in processes that affect atomic nuclei (dense cores of atoms) - It is dis nct from the energy of other atomic phenomena such as ordinary chemical reac on, which involve only the orbital electrons of atoms Method of Releasing Nuclear Energy - Controlled nuclear fission in devices called reactors Reactors - Which now operate in many parts of the world for the produc on of electricity Method for Obtaining Nuclear Energy - Controlled nuclear fusion (but has not been perfected by 2020. Nuclear Energy - Has been released explosively by both nuclear fusion and nuclear fission - Notable applica on through nuclear power plants Nuclear Power - A clean and efficient way of boiling water to make steam, which turns turbines to produce electricity Nuclear Power Plants - Use low-enriched uranium fuel to produce electricity through a process called fission---the spli ng of uranium atoms in a nuclear reactor. Uranium - Fuel consists of small, hard ceramic pellets that are packaged into long, ver cal tubes. - Bundles of this are inserted into the reactor. Radioac vity - A phenomenon that occurs in a number of substances - Atoms of the substances spontaneously emit invisible but energe c radia ons, which can penetrate materials that are opaque to visible light - The effects of these radia ons can be harmful to living cells but, when used the right way, they have wide range of beneficial applica ons. Radia on Chronicle  400 BC  Greece  Democritus  Proclaims all material things are made of ny par cles, “atoms,” or “not divisible.”  1789  Uranium  Mar n Klaproth  1869  Dmitri Mendeleev  Periodic law of elements evolved to the Table of Elements  1885  Balmer  Empirical formula  Gives the observed wavelength of hydrogen light spectra. 1  =𝑅 −  1890  Thorium  First used in mantles for camping lanterns  1895  Wilhelm Roentgen  X-rays  Medical Poten al  Nobel in 1901  November 8  1896  Henri Becquerel  “Some atoms give off energy in the form of ways. Uranium gives off radia on.”  Radioac vity  February 26  Nobel Prize with Pierre Curie  1897  J.J. Thomson  Electron  1898  Marie and Pierre Curie  Radioac ve Elements  Radium  Polonium  Marie Curie  Named radioac vity  Nobel Prize 1911 for the discovery of radium and polonium  1899  Ernest Rutherford  Nobel Prize 1908  Radia on can be divided into two types: 1. Alpha Rays 2. Beta Rays  1900  Pierre Curie  Gamma Rays (Radia on)  Nobel Prize 1903  Becquerel  1905  Albert Einstein  Theory between mass and energy  𝑒 = 𝑚𝑐  Nobel Prize 1919  Photoelectric effect  1911  Ernest Rutherford  Most of an atom  Empty space  Iden fies the atomic nucleus  1911  George de Hevesy  Using Radio Tracers  Medical diagnosis  Nobel Prize 1943  1913  Niels Bohr  First atom model  Mini solar system  1913  Hans Geiger  Geiger Counter from measuring radioac vity  1913  Frederick Proescher  The first study on the Intravenous Injec on of Radium for the therapy of various diseases  1920  Ernest Rutherford  Proton  1927  Hermann Blumgart  Boston physician  First uses radioac ve tracers to diagnose heart disease  1932  James Chadwick  Neutron  Nobel Prize 1935  1932  Ernest O. Lawrence and M. Stanley Livingston  Publish the first ar cle on “the produc on of high-speed light ions without high voltages.”  1939  E. Lawrence  A milestone in the produc on of usable quan es of radionuclides  Nobel Prize 1939  For the cyclotron  1934  Irene and Frederic Joliot-Curie  Ar ficial radioac vity  Nobel Prize 1935  For crea ng the first ar ficial radioac ve isotope  1935  Nuclear medicine  comes into existence when cyclotron-produced radioisotopes and nuclear radia on become available in the U.S.  1936  John H. Lawrence  The brother of Ernest  Makes the first clinical therapeu c applica on of an ar ficial radionuclide when he used phosphorus-32 to treat leukemia.  1937  John Livingood and Glenn Seaborg  Iron-59  Iodine-131 and Cobalt-60  1938  All isotopes currently used in nuclear medicine  Nobel Prize 1951  G Seaborg and MacMillan  1938  O o Hahn and Fritz Strassman  Produce lighter elements by bombarding uranium with neutrons  Irene Joliot-Curie and Pavle Savich  No ce the same effect  Lise Meitner and O o Frisch  Fission  Recognized it as spli ng of the atom  Nobel Prize 1944  O. Hahn  1938  Enrico Fermi  Nobel Prize  For the produc on of new elements by neutron radia on  1939  The principles of nuclear reactors were first recorded and sealed in an envelope.  It remains secret during the WWII  1939  Emilio Serge and Glenn Seaborg  Techne um-99m  An isotope currently used in nuclear medicine  1939  U.S. Advisory Commi ee on Uranium  Recommends a program to develop an atomic bomb  Later called the Manha an Project  1940  Rockefeller Founda on  Funds the first cyclotron dedicated to biomedical radioisotope produc on at Washington University in St. Louis  1942  Manha an Project  Formed to build the atomic bomb before the Nazis secretly  1942  Fermi  Demonstrated the first self-sustaining nuclear chain reac on in a lab at the University of Chicago  1942  The United States  Drop atomic bombs on Hiroshima and Nagasaki  Japan surrenders First Reports of Injury Elihu Thomson - Late 1986 - Burns from deliberate exposure of a finger to X-rays Edison’s assistant - Hair fell out and scalp became inflamed and ulcerated Mihran Kassabian - 1870-1910 Sister Blandina - 1871-1916 - 1898 o Started work as a radiographer in Cologne and held nervous pa ents and children with unprotected hands. o Controlled the degree of hardness of the X-ray tube by placing her hand behind the screen. o A er 6 months, she suffered from strong flushing and swellings of hands and was diagnosed with an X-ray cancer. o Some of her fingers were amputated, and it worsened un l her whole hand and arm were amputated. - 1915 o She suffered difficul es breathing, and her X-ray examina on showed an extensive shadow on the le side of her thorax. o She also had a large wound on her whole front and back side - Died on 22nd October 1916 First Radiotherapy Treatment - Emil Herman Grubbe o Conducted on January 29, 1896, to a woman (50) with breast cancer - The treatment consisted of 18 daily 1-hour irradia on. - The pa ent’s condi on was relieved, but she died shortly a erward from metastases. Radia on Protec on - Early Protec ve Suit o Lead glasses o Filters o Tube shielding o Early personal “dosemasters” - Roentgen Social of Inquiry o 1898 - 1915 o Roentgen Society publishes recommenda ons - 1921 o The Bri sh X-ray and Radia on Protec on Commi ee established and issued reports - 1928 o 2nd Interna onal Congress of Adopts Bri sh recommenda ons plus the Roentgen - 1931 o USACXRP publishes the first recommenda ons (0.2 r/d) - 4th ICR o Adopts 0.2 Roentgens per day limit Life Span Study - 94,000 persons o > 50% are s ll alive in 1995 - 1991 o About 8,000 cancer deaths, approximately 430 of these a ributable to radia on. - 21 out of 800 in utero with dose o >10 mSv severely mentally retarded individuals have been iden fied - No increase in hereditary disease Atomic Theory Part 1: Rutherford – Birth of Planetary Model  1900  Alpha Rays  Beta Rays  Gamma Rays  1909  Rutherford  Conclude from bombarding thin gold foils with alpha par cles (PO(214-84))  Large angle deflec on seen in 1/8000 alpha par cles suggests the existence of a very small and massive nucleus  Proposed the planetary model  𝑅𝑛𝑢𝑐 ≈ 1.3 𝐴 × 10 𝑚  𝑅𝑎𝑡𝑜𝑚 ≈ 1.5 × 10 𝑚 Part II: Bohr’s Hydrogen Atom  1913  Was not sa sfied with classical mechanics in the planetary model  It is an unstable model since an accelerated charge will emit light and therefore lose energy  Postulates the first semi-classical model  The angular momentum of the electron is quan zed:  𝑚𝑣𝑟 = 𝑛ℎ  Energy and orbital radii are also quan zed:.  𝑟 = (𝐴).  𝐸 = (𝑒𝑉) Problem with Bohr’s model and classical mechanics - Could only predict correctly the energy levels of H - Classical mechanics could not explain the dual behavior of light (par cle and wave) - The approach of Bohr of mixing classical mechanics and quan zing certain variables was suddenly heavily used o Other accurate predic ons were made with new semi-classical or rela vis c models  o Prelude for Quantum Mechanics Birth of Quantum Mechanics - 1925 - Simultaneously and independently o Heisenberg actually realized that the reason Bohr’s model failed was that it was trying to predict no observable variables, which are:  Posi on  Speed o Heisenberg actually created a model focusing on measurable variable  Balm Wavelength  showed that 𝐷𝑝. 𝐷𝑥 ≥ ħ 𝑜𝑟 𝐷𝐸. 𝐷𝑡 ≥ ħ  Heisenberg Uncertainty Principle o Sta ng that it is impossible to measure precisely the speed and loca on of a par cle  Also showed that x.px was different from px.x o Others showed in this typical matrix property called the Heisenberg model of Matrix Mechanics. o Schrödinger  Established a law defined by a differen al equa on that describes ma er as a wave (D2X and Dt)  Later, his equa on will be formalized by linear algebra and matrix simplifica on Nuclear Chemistry: Basics Nuclear Terminology  Nuclide  An atom with a specific number of protons in its nucleus  There are 27 stale nuclides in nature. Others are radioac ve  Nucleon  Proton or neutron, especially as part of an atomic nucleus  Unstable Isotope  Naturally or ar ficially created isotopes have an unstable nucleus that decays, emi ng alpha, beta, or gamma rays un l stable.  Radionuclide  An unstable isotope that undergoes nuclear decay  All isotopes of elements with ≥ 84 protons are radioac ve  Specific isotopes of lighter elements are also radioac ve (e.g. 𝐻)  # of Nucleons = # of Protons + # of Neutrons Chemical Reac on  Break and form bonds between atoms but elements remain the same   Nuclei are unchanged.  Nuclear reac ons  Differ from ordinary chemical reac ons  Atomic numbers of nuclei  May change (elements are converted to other elements, or an element can be converted to an isotope of that element)  Protons, neutrons, electrons, and other elementary par cles  May be involved in a nuclear reac on  Reac ons  Occur between par cles in the nucleus  Ma er  Is converted to energy, and huge amounts of energy are released  Nuclear reac ons  Involved a specific isotope of an element  Different isotopes of an element  May undergo different nuclear reac ons Special Nota on to Describe Nuclear Par cles 𝑋 X = element symbol A = is the mass number = total number of protons and neutrons in the nucleus Z = is the atomic number = total number of protons in the nucleus – determines iden ty of element Examples:  𝐶 Carbon with 6 neutrons (12 – 6 = 6 neutrons)  𝐶 Carbon with 7 neutrons (13 – 6 = 7 neutrons)  𝑈 Uranium with 143 neutrons (235 – 92 = 143)  𝑈 Uranium with 146 neutrons (238 – 92 = 146) Neutrons  Acts as a glue to hold the nucleus together  For the smaller elements  The ra o of neutrons to protons is ~1: 1  As the size of the nucleus increases  The ra o of neutrons to protons increases to ~2: 1 Nuclear Stability  Unstable isotope  Emits some kind of radia on that is radioac ve  Stable isotope  Does not emit radia on  If it does, its half-life is too long to have been measured.  Stability of the nucleus of an isotope  Determined by the ra o of neutrons to protons.  Observa on of the atomic number of isotopes  Isotopes with atomic number (Z) > 82  Are unstable  Elements with atomic number (Z) < 82  Have one or more stable isotopes  Except techne um (Z = 43) and promethium (Z = 61)  Do not have any stable isotopes  Isotopes with atomic number (Z) ≤ 20 and with a neutron (n) to proton (p) ra o of about 1, are more likely to be stable (𝑛 ÷ 𝑝~1)  Observa ons on whether the nucleus contains odd or even numbers of protons and neutrons leads us to believe that a nucleus with:  Odd # of protons and odd # of neutrons  Is most likely to be unstable  Even # of protons and even # of neutrons  Is most likely to be stable  Nuclei containing 2, 8, 20, 50, 82, or 126 protons or neutrons  Are generally more stable than nuclei that do not possess these magic numbers  As the atomic number increases  More neutrons are needed to help bind the nucleus together, so there is a high neutron-to- proton ra o. # protons # neutrons # stable nuclei Even Even 164 Even Odd 53 Odd Even 50 Odd Odd 4 Band of Stability Nucleus - Stable if it cannot be transformed into another configura on without adding energy from the outside. Nuclides - Out of the thousands of these only about 250 are stable. Stable Nuclei - Stable isotopes fall into a narrow band o Which is called the band of stability  Belt, zone, or valley of stability Lighter Stable Nuclei - Have equal numbers of protons and neutrons Heavier Stable Nuclei - Increasingly more neutrons than protons. - Have more proton-proton repulsions - Require larger numbers of neutrons to provide compensa ng strong forces to overcome these electrosta c repulsions and hold the nucleus together. All isotopes of elements with atomic numbers greater than 83 - Unstable Solid line - A line where n = Z Radioac vity - Unstable isotopes decompose (decay) by a process - Natural Radioac vity o A few such nuclei occur in nature - Many more can be induced ar ficially by bombarding stable nuclei with high-energy par cles. Types of Radioac vity  Alpha Emission  𝑎  𝐻𝑒  𝑎 par cles  Have high energy and low speed  Posi vely charged  Common for heavier radioac ve isotopes Note: - a balanced nuclear equa on = conserva on of atomic number and mass number - Not concerned with charge considera ons in nuclear reac ons, because they do not affect the reac vity or the transforma on products  Beta Emission  𝛽  𝑒  𝛽 par cle  An electron  Occurs when a neutron is converted to a proton and an electron (emi ed from nucleus) 