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Nuclear Chemistry

Nuclear Chemistry. Radioactive Decay. The Nucleus. IT’S TINY ( tiny! ) radius≈ 10 -13 cm Extremely Dense ~ 1.6 x 10 14 g/mL Made of nucleons (neutrons and protons). Isotopes. Recall:. Mass Number. Element Symbol. Atomic Number (From periodic table).

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Nuclear Chemistry

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  1. Nuclear Chemistry Radioactive Decay

  2. The Nucleus • IT’S TINY (tiny!) radius≈ 10-13 cm • Extremely Dense ~ 1.6 x 1014 g/mL • Made of nucleons (neutrons and protons)

  3. Isotopes • Recall: Mass Number Element Symbol Atomic Number (From periodic table) Atoms that have identical atomic numbers but different mass numbers are called isotopes Example: The common isotopes of Carbon are:

  4. Radioactive Decay • Radioactive: Nuclei that spontaneously decompose • Form a different nucleus • Produce one or more particles • Described by a nuclear equation: • Ex/ • Both atomic number and mass number are conserved • All nuclides w/ 84 protons or more are unstable • Light nuclides are stable when Z = A-Z (1:1 p/n ratio) p. 879 +

  5. Alpha Decay α • Alpha Particle: Helium nucleus • Alpha particle production = common form of radioactive decay for heavy elements. • Ex/ Thorium-230 decay +

  6. α-decay Helium Nucleus

  7. Beta decay β • Beta Particle: an electron • Beta particle production = most common type of decay in which the mass number remains constant • The net effect of β-particle production is changing a neutron to a proton • Ex/ Iodine-131 decay +

  8. β-decay Same # of nucleons  changed a neutron to a proton (Think of a neutron is a proton and an electron)

  9. Gamma ray production γ • Gamma ray: a high energy photon • (photon=basic “unit/particle” of EM radiation) • Release of gamma rays is a way for a nucleus w/ excess energy to reach its ground state • Often accompanies nuclear decay (like alpha-decay) • Ex/ Uranium-238 decay + + 2

  10. Positron Production + Beta decay with gamma ray production Gamma ray production with no change to isotope (nucleons are packed more tightly together)

  11. Radiation Penetration

  12. Positron Production • Positron: particle w/ same mass as electron but opposite charge • Occurs when neutron/proton ratio is too small (below the “zone of stability”) • The net effect of positron production is changing a proton to a neutron • Ex/ Sodium-22 decay +

  13. Electron Capture e- • Electron: • Occurs when an inner orbital electron is captured by the nucleus • Gamma rays are always released with electron capture to get rid of excess energy • Ex/ + +

  14. Practice • Chapter 18 • 9-12; 15&16

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