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Nuclear Chemistry

Nuclear Chemistry. Section 1: Basic Definitions. Nuclear Chemistry The study of the atomic nucleus, its reactions and radioactivity Radioactivity Spontaneous emission of particles and/or energy during nuclear decay. Section 1, continued. Nuclear Decay

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Nuclear Chemistry

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  1. Nuclear Chemistry

  2. Section 1: Basic Definitions • Nuclear Chemistry • The study of the atomic nucleus, its reactions and radioactivity • Radioactivity • Spontaneous emission of particles and/or energy during nuclear decay

  3. Section 1, continued • Nuclear Decay • Spontaneous disintegration of a nucleus • Results in a new element being formed • Occurs when particles and/or energy escape from an unstable nucleus • Releases large amounts of energy • Radiation • Can refer to either the particles or energy released during nuclear decay

  4. Section 2: Types of Radiation to Know Radiation Description Radiation Symbol Proton: Neutron: n Electron: e, β- • Proton • Positively charged particle in the nucleus of the atom • Hydrogen nucleus • Most cosmic rays are protons traveling at the speed of light • Neutron • Neutral particle in the nucleus of the atom • Electron (Beta-minus particle) • Negatively charged particle that moves randomly in specific orbitals outside the nucleus of an atom

  5. Section 2, continued Radiation Description Radiation Symbol Positron: e, β+ Alpha: He, α Gamma: γ • Positron (Beta-positive particle) • Anti-matter electron • Same properties of an electron except it has a positive charge • Alpha Particle • Helium nucleus • 1st radioactive particle discovered by Ernest Rutherford • Gamma Radiation • High energy electromagnetic radiation

  6. Section 3: Properties of Certain Types of Radiation

  7. Section 4: Isotopes • Same element, different number of neutrons • There are 2 ways to identify isotopes: • Hyphen-Notation = element – mass # • Example: oxygen – 16 • Chemical Configuration • Example:

  8. Section 4, continued • Isotopes of hydrogen have special names • Deuterium and tritium are radioactive; protium is not.

  9. Section 4, continued • Why are some isotopes radioactive and others are not? • The proton : neutron ratio determines whether an isotope is radioactive • Elements with atomic # ≤ 20 prefer a 1 : 1 ratio • Elements with atomic # > 20 prefer a 1 : 1.5 ratio • Transuranium elements = • Elements with atomic # > uranium (92) • All are radioactive • In fact, all elements with atomic number > 83 are radioactive!

  10. Section 4 Example Problems • Write the hyphen-notation and the chemical configuration for an iron atom that has 23 electrons and 32 neutrons.

  11. Section 4 Example Problems, continued • Write the hyphen-notation and determine the number of protons, neutrons and electrons for P.

  12. Section 4 Example Problems, continued • Write the hyphen-notation and chemical configuration for the three isotopes of hydrogen. Assume each isotope is neutral.

  13. Section 5: Use of Carbon-14 in Radiocarbon Dating

  14. Section 6: Nuclear Reactions v Chemical Reactions Nuclear Reactions Chemical Reactions Forms new substances based on the elements present in the reactants Small energy changes Energy comes from breaking and forming chemical bonds Involves valence electrons • Forms a new isotope or different element • Extremely large energy changes • Energy comes from the binding energy of the nucleus • Involves a change in the number of protons or neutrons

  15. Section 7: Writing Nuclear Reactions Steps Example + _________ Mass #s: 29 = 0 + _____ Atomic #s: 12 = -1 + _____ • Set up 2 equations: one using the mass (top) numbers and the other using the atomic (bottom) numbers. • Calculate the missing mass number. • Calculate the missing atomic number. • Use the atomic/mass #s to determine the identity of the missing particle.

  16. Section 8: Alpha Emission • A helium nucleus (2 p, 2 n) is emitted from the nucleus • Example: Alpha decay of 241Am

  17. Section 8: Beta Emission • A neutron is converted into a proton and electron, then the electron (β- particle) is emitted • Example: Beta decay of 14C

  18. Section 8: Positron Emission • A proton is converted into a neutron and positron, and the positron is emitted from the nucleus • Example: Positron Emission of 11C

  19. Section 8: Electron Capture • The nucleus captures an electron and combines it with a proton to form a neutron • Example: Electron capture by 7Be

  20. Pu* Pu Section 8: Gamma Emission γ ray • Gamma rays are emitted during nuclear reactions, either alone or with other types of radiation • Gamma rays do NOT change the mass number or atomic number because they are energy not matter.

  21. Section 9: Decay SeriesA series of nuclear reactions that occur until a stable nucleus is formed The first 4 nuclear reactions in the uranium-238 decay series are: 238U 42He + 234Th 234Th 0-1β + 234Pa 234Pa 0-1β + 234U 234U 42He + 230Th

  22. Section 10: Fission • Definition • heavier nuclei split apart to form lighter nuclei • Occurs in… • Nuclear power plants, nuclear bombs • Chain Reaction (definition) • neutrons produced from one reaction can hit other isotopes to start a new fission reaction • Example of Fission Reaction +  + + 3

  23. Section 11: Nuclear Power Plant Containment Structure (A) -thick layers of concrete and steel to prevent radiation leakage Control Rods (B) -controls the rate of reaction; can be used to shut reaction down Reactor (C) -where the nuclear reactions take place Steam Generator (D) -nuclear reactions produce heat energy which is used to boil water Turbine (H) -steam runs the turbine, which causes the generator (G) to produce electricity Fuel Rods (K) -usually contain uranium-235; the fuel for the nuclear fission reaction  Condenser (I) -sends cool water to the cooling tower (J) and reactor; vital to keep reactor from overheating

  24. Section 11: Nuclear Power Plant • A nuclear reactor is self-sustaining due to the chain reaction. The neutrons that are produced from one reaction cause a new fission reaction to occur.

  25. Section 12: Nuclear Power (Fission) Pros and Cons Pros Cons Expensive to build and maintain Risk of accidents Security Thermal pollution (warm water into streams and rivers) Disposal of nuclear waste (must be buried for possibly thousands of years) • No air pollution • No greenhouse gas emissions • Low cost fuel because very little is needed • Can be done at room temperature

  26. Section 13: Fusion Reaction • Definition • light nuclei combine (fuse) together to form heavier nuclei • Occurs in… • the sun and other stars; hydrogen (fusion) bomb • Example of Fusion Reaction +  +

  27. Section 14: Fusion Pros and Cons Pros Cons Does not sustain a chain reaction. Requires extremely high temperatures (108 - 109 °C) and pressures. We do not have the technology to efficiently harness the energy produced by fusion or to contain a fusion reaction. • Produces even more energy per gram of fuel than fission. • Produces less nuclear waste than fission. • Fusion fuel is easy to get. (Heavy hydrogen is found in water.)

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