lecture 1 - Chemistry 312 Summer 2011 Tracy Furutani...

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Chemistry 312 Summer 2011 Tracy Furutani University of Washington
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What is inorganic chemistry? Basically, the chemistry of the rest of the periodic table not involved with carbon Mostly emphasizing the d-block elements Involves bulk properties and reactivity of these elements Note: Z = atomic number = number of protons in nucleus
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Where did it all come from? Big Bang: 12.8 ± 2.0 by, in which a singularity expands, generating all wavelengths of radiation Eventually, the energy density and temperature reduce to allow stable subatomic particles Eventually, the temperature and pressure reduce to allow atom formation: initial composition about 75% H and 25% He
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Where did the rest of the elements come from? Part 1 Gravity generates local concentrations of matter, called stars. Stars’ cores are dense enough to allow the proton-proton cycle (aka hydrogen fusion) to occur; the result is helium-4 nuclei When hydrogen nuclei run low in stars, helium nuclei fuse in the triple-alpha process to generate carbon-12 nuclei
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A side note on stability The “nuclear binding energy” (NBE) measures the difference in energy between the reactants and products of a fusion process. For the proton-proton cycle and triple- alpha process, the products of fusion weigh less than the reactants; the “missing” mass is converted to energy (E = mc 2 ) and that energy is how much the product nuclei are more stable: thus, the NBE
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Where did the rest of the elements come from? Part 2 Thus stars generate a lot of excess energy through fusion; this excess energy, which pressurizes the stellar gases, prevents gravity from collapsing the gases to the core And thus the CNO cycle is another proton-fusing process that generates energy Diminishing returns: as heavier nuclei are generated, the NBE between reactants and products becomes smaller At Z = 26 (iron nuclei), heavier nuclei require energy for generation, so stellar fusion stops at iron
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Where did the rest of the elements come from? Part 3 Our Sun will cease fusion upon the generation of carbon-12 nuclei and simply cool off its core as a “white dwarf” Stars with masses twice the Sun will generate iron nuclei; the extra mass, once fusion ceases, will collapse to the core at speeds near the speed of
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lecture 1 - Chemistry 312 Summer 2011 Tracy Furutani...

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