Chapter_15_Nucl_chem_Part_2_

Chapter_15_Nucl_chem_Part_2_ - Chapter 15 part 2 Nuclear...

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Exam III: chapter 14 and chapter 15 Periodic Table on the web http://pearl1.lanl.gov/periodic/default.htm -------------------- Chapter 15, part 2 Nuclear Chemistry
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Nuclear symbol A Z X Z = the atomic number , the number of protons (we look this up in the periodic table) The number of protons also defines the number of positive charges in an element A = the mass number , the number of protons plus neutrons --- Examples: 4 2 He 232 90 Th 228 88 Ra 14 6 C
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Band of Stability In a plot of N vs. Z, stable nuclides are distributed within a specific band (blue dots) Atoms that fall outside the stability band are unstable Nuclides heavier than Bi-209 are unstable (Z= 83 N= 126) Unstable nuclides are radioactive o They undergo nuclear decay reactions ---
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Radioactive elements emit radiations Penetrating Ability of Types of Radiation ---- Nuclear emissions also include positrons (not shown in that experiment)
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Alpha emission Emission of an α particle removes 2 protons and 2 neutrons from a decaying nuclide a nucleus with 2 protons and an atomic mass of 4 corresponds to the nucleus of Helium Symbols for alpha particles 4 2 He 4 2 α or ----
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As the consequence of emission of an alpha particle from Th-232, another chemical element is produced (Ra-228) To identify unknowns in nuclear equations, we should write balanced equations o Keep track of the number of protons, neutrons, and charges --------------- Example of a nuclear decay 232 90 Th 228 88 Ra 4 2 α +
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Thorium has 90 protons When an atom emits an alpha particle it loses 2 protons and 2 neutrons Let X denote the unknown
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Chapter_15_Nucl_chem_Part_2_ - Chapter 15 part 2 Nuclear...

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