Electronic Configuration Chemical Bonding CoordinationElectronic Configuration of the ElementsTransition ElementsInformation on Transition Elements or Why do we care?Oxidation of IronBonding in mineralsIonic BondingCovalentSi-O bondSlide 10Slide 11Metallic BondVan der WaalsPolar Bonding or Hydrogen BondingCoordination Number C.N.Radius RatioCoordination Number vs Radius RatioLet’s calculate one of the radius ratiosSome words you need to knowPauling’s RulesElectronic ConfigurationChemical BondingCoordinationElectronic Configuration of the Elementswww.nutrisci.wisc.edu/NS623/electronic.pdfWhat determines how electrons are distributed?Pauli Exclusion PrincipleHund’s RuleGood web site: http://www.science.uwaterloo.ca/~cchieh/cact/c120/eleconfg.htmlTransition ElementsInformation on Transition Elementsor Why do we care?http://library.thinkquest.org/3659/pertable/trametal.htmlOxidation of IronFe +2Fe +3Ferrous FerricReduced OxidizedReduction is the gain of electronsOxidation is the loss of electronsBonding in mineralsIonicCovalentMetallicVan der WaalsPolarIonic BondingNaCl (halite or rock salt)Na+ and Cl- have noble gas configurationElectrostatic attraction bonds them togetherMinerals with ionic bonds have moderate H and G, have high melting points and are poor conductors of electricity and heatStrength is proportional to the electronic attractionBond is non-directionalCovalentSharing of electronsStrongest of chemical bondsDo not yield ions in solutionBonds are directionalExample: diamond CSi-O bondIs about 50% covalent and 50% ionicElectronegativity—power of an atom to attract. Compounds made of elements with very different values of electronegativity are more ionic than compounds made of elemts clost to each other in electronegativityy = 1 - exp(-0.25 * x2) (Pauling, 1948)Metallic BondMany electrons owe no allegiance to any particular nucleus and are free to “drift”Good conductorsUsually low hardness and melting pointsExamples include native metals such as Cu, Ag, and AuMinerals may have qualities of several types of bonds: galena ionic and metallicVan der WaalsDipoles of moleculesUsually found in gases and liquids, rare in mineralsExample is graphite CPolar Bonding or Hydrogen BondingExamples include micasCoordination Number C.N.# of anions that can fit around a cationNaCl 6CaF28Radius RatioThis is the ratio of the radius of the cation to that of the anionThis ratio usually determines the CN of the cationCoordination Number vs Radius RatioCN RR CN RR CN RR CN RR CN RR CN2 3 4 6 8 12.155 .225 .414 .732 1Make sure you remember to give examples on the boardLet’s calculate one of the radius ratiosUse triangular coordinationHandout or on board!Some words you need to knowCN=4 tetrahedralCN=6 octahedralCN=8 cubicPauling’s
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