* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download NUCLEAR CHEMISTRY PACKET - Student
Survey
Document related concepts
Fallout shelter wikipedia , lookup
Muon-catalyzed fusion wikipedia , lookup
Background radiation wikipedia , lookup
Ionizing radiation wikipedia , lookup
Nuclear and radiation accidents and incidents wikipedia , lookup
Isotopic labeling wikipedia , lookup
Nuclear fusion wikipedia , lookup
Nuclear fission wikipedia , lookup
Nuclear fusion–fission hybrid wikipedia , lookup
Nuclear fission product wikipedia , lookup
Technetium-99m wikipedia , lookup
Radioactive decay wikipedia , lookup
Nuclear binding energy wikipedia , lookup
Nuclear drip line wikipedia , lookup
Valley of stability wikipedia , lookup
Transcript
NUCLEAR CHEMISTRY Text Book Chapter 25 OBJECTIVES Stability of isotopes is based on the ratio of neutrons and protons in its nucleus. Although most nuclei are stable, some are unstable and spontaneously decay, emitting radiation. (3.1o) Each radioactive isotope has a specific mode and rate of decay (half-life). (4.4a) A change in the nucleus of an atom that converts it from one element to another is called transmutation. This can occur naturally or can be induced by the bombardment of the nucleus by high-energy particles. (5.3a) Spontaneous decay can involve the release of alpha particles, beta particles, positrons and/or gamma radiation from the nucleus of an unstable isotope. These emissions differ in mass, charge, and ionizing power, and penetrating power. (3.1p) Nuclear reactions include natural and artificial transmutation, fission, and fusion. (4.4b) There are benefits and risks associated with fission and fusion reactions. (4.4f) Nuclear reactions can be represented by equations that include symbols which represent atomic nuclei (with the mass number and atomic number), subatomic particles (with mass number and charge), and/or emissions such as gamma radiation. (4.4c). Energy released in a nuclear reaction (fission or fusion) comes from the fractional amount of mass converted into energy. Nuclear changes convert matter into energy. (5.3b) Energy released during nuclear reactions is much greater than the energy released during chemical reactions. (5.3c) There are inherent risks associated with radioactivity and the use of radioactive isotopes. Risks can include biological exposure, long-term storage and disposal, and nuclear accidents. (4.4e) Radioactive isotopes have many beneficial uses. Radioactive isotopes are used in medicine and industrial chemistry, e.g., radioactive dating, tracing chemical and biological processes, industrial measurement, nuclear power, and detection and treatment of disease. (4.4d) DISCOVERY OF RADIOACTIVITY ____________________ was familiar with Wilhelm Conrad Roentgen’s accidental discovery of mysterious rays in 1895 and chose to study related phenomenon. In March 1896, due to some bad weather, Becquerel was unable to use the sun for his external energy source for his experiments. He put his photographic plates away in a drawer which also happened to contain some uranium containing crystals. The plates were exposed, suggesting that the crystals emitted rays on their own! _____________________________ discovered Polonium and introduced the term “radioactive”. Marie Curie suggested that radiation is an atomic property of matter – not an independent emanation. In 1899 _________________________ discovered that uranium compounds produce three different kinds of radiation. He separated the radiation according to their penetrating abilities and named them α (alpha), β (beta) and γ (gamma) after the first three letters in the Greek alphabet. STABILITY OF NUCLEI Nuclei are composed of combinations of ______________ and _______________. The ratio of these nucleons determines the stability of any given nucleus. Most nuclei are stable, but some are unstable. Stable isotopes have between a 1:1 and 1.5:1 ratio of protons and neutrons. Most unstable isotopes have twice as many neutrons as protons. Unstable nuclei will spontaneously decay, emitting ______________________. All elements with an atomic number higher than 83 are radioactive. TYPES OF DECAY See Table O for Symbols Used in Nuclear Chemistry ALPHA DECAY An alpha particle is a ___________ nucleus, with2 protons and 2 neutrons. It is represented by the symbol __________ or __________. Alpha radiation can be stopped by a piece of paper. It has ___ penetrating power. Because the alpha particle contains 2 protons, when an atom releases an alpha particle, its atomic number would decrease by __________. This means it is a new element!!!! Consider radium-226: Before the decay After alpha decay Number of protons Number of neutrons Total mass Number of protons Number of neutrons Total mass What happened to the atomic number? _________________ What happened to the mass number? _________________ Writing this as an equation, to the left of the arrow we write the symbol for the atom before the decay. To the right of the arrow we write the symbol for the atom that remain AND the radiation that was emitted. Ra BETA DECAY A beta particle is equivalent to an _________ (as a neutron converts to a proton). n p +e It is represented by the symbol _________ and has a charge of __________. It has a ______________ penetrating power, needing ~6mm of aluminum to stop most beta particles. Consider lead-214: Before the decay After beta decay Number of protons Number of neutrons Total mass Number of protons Number of neutrons Total mass What happened to the atomic number? _________________ What happened to the mass number? _________________ Write the equation: Pb GAMMA DECAY A gamma ray is a wave of energy, (not a particle) resulting from an energy change within the nucleus. It has no mass or charge. Gamma radiation doesn’t change the state of the nucleus, it just carries some energy away. Gamma rays are emitted along with alpha or beta particles. Gamma rays have ________ penetrating power. It takes a thick sheet of metal, such as lead, or concrete to reduce them significantly. POSITRON EMISSION A positron is emitted during the conversion of a proton to a neutron. p n + e It is represented by the symbol _________ and has a charge of __________. Consider potassium-37: Before the decay After positron decay Number of protons Number of neutrons Total mass Number of protons Number of neutrons Total mass What happened to the atomic number? _________________ What happened to the mass number? _________________ Write the equation: Particle Alpha Beta Positron Gamma K Mass Charge 4 amu +2 0 amu -1 0 amu +1 0 amu None Symbol Penetrating Power Low Moderate Moderate High NUCLEAR EQUATIONS Nuclear reactions can be represented by equations that include symbols which represent atomic nuclei (with mass number and atomic number), subatomic particles (with mass and charge) and emitted particles. REMEMBER: The masses on both sides of the equation must be equal The charges on both sides of the equation must be equal 222 1. 86 4 Rn ---------> ________ + 234 2. ______ ---------> 3. Th ---------> 90 4 90Th 230 + 88Ra + ______ 5. 0 Pb ---------> ______+ 82 234 92 U ---------> 2He 226 214 4. 2He -1e 234 93Np + _______ Determine the type of emission given off by each element by looking at TABLE N. Try writing equations for the following emissions: 235U 232Th 60Co Iron-53 TRANSMUTATIONS A change in the nucleus of an atom changes it to a new type of atom (i.e. a new element). This is called ______________________. Transmutation can occur naturally or artificially. Spontaneous decay can involve the release of different particles from the nucleus. ___________________ transmutation requires the bombardment of a nucleus by high energy particles. FISSION Nuclear fission occurs when the heavy nucleus of an atom is split into two lighter nuclei, releasing neutrons and energy. This can be initiated artificially by "shooting" the nucleus with a neutron. The lighter elements that form are more stable. U + n Ba + Kr + n + Energy Since neutrons are released, they can be captured by other uranium atoms causing them to split. This results in a _______________________, which can be controlled (as in the case of a nuclear reactor) or uncontrolled (atomic bomb). NUCLEAR POWER PLANT Boiling Water Reactor (BWR) The boiling water reactor operates in essentially the same way as a fossil fuel generating plant. In the BWR fission produces he heat that boils water in the reactor core. Steam from the boiling water powers a turbine that drives a generator to produce electricity. The reactors at northeastern Japan’s Fukushima Naiishi plant damaged in the March 2011 earthquake and tsunami are BWRs. Pressurized Water Reactor (PWR) In the PWR plant, a pressurizer unit keeps the water that is flowing through the reactor vessel under very high pressure to prevent it from boiling. The hot water then flows into the steam generator where it is converted to steam. The steam passes through the turbine which produces electricity. About two-thirds of the reactor power plants in the U.S. are of the PWR type. FUSION Nuclear fusion combines two light nuclei to form heavier nuclei. Nuclear fusion is the process that powers the sun. The mass of the new nucleus formed by fusion is less than the sum of the two reactants. The difference in mass was converted to energy. E = mc2 To do this, nuclear fusion requires very high temperatures, and is not yet ready for practical use. Deuterium-tritium reaction H + H He + n + Energy HALF-LIFE Each isotope has a specific mode and rate of decay. (see Table N) The rate of decay is called __________________. It is the time required for half of the atoms in any given quantity of a radioactive isotope to decay. Half-life is a ____________________ that can never be changed. For example, the half life of U-238 is __________________. That means, in 4.5 billion years half of the uranium-238 on earth will have decayed into other elements. In another 4.5 billion years, half of the remaining uranium-238 will have decayed. One fourth of the original material will remain after 9 billion years. X grams ---------- X/2 grams ---------- X/4 grams ----------- X/8 grams 1half life 2nd half life 3rd half life ½ of sample still radioactive after 1 half life ¼ of sample still radioactive after 2 half lives 1/8 of sample still radioactive after 3 half lives # OF HALFLIVES AMOUNT REMAINING TIME ELAPSED MASS OF SAMPLE USES AND DANGERS OF RADIOISOTOPES USES Radioactive isotopes may be used in: RISKS The risks associated with using radioactive isotopes include: VOCABULARY Alpha particle Artificial transmutation Atomic number Beta particle Chain reaction Decay Emit Fission Fusion Gamma ray Half-life Isotope Mass number Natural transmutation Nucleon Positron Radioisotope Tracer Transmutation NAME: _______________________________________ NUCLEAR BIG IDEAS UNSTABLE NUCLEUS NATURAL DECAY Particle Alpha Beta Positron Gamma Mass Charge Symbol Penetrating Power EQUATIONS Conservation of mass & charge ARTIFICIAL DECAY FISSION Controlled Uncontrolled FUSION HALF LIFE # OF HALFLIVES AMOUNT REMAINING USES & RISKS REFERENCE TABLES Table O Table N TIME ELAPSED MASS OF SAMPLE