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Unformatted text preview: Exam 2 Chem 4011/5011 November 17, 2009 1. Alkali metals have the largest metallic radii of the elements and crystallize in a body‐ centered cubic lattice. The coinage metals Cu, Ag, and Au have relatively small metallic radii and crystallize in a cubic‐closest packed structure. In which lattice is packing efficiency greatest? How many nearest‐neighbors surround metal atoms in the two structures? 2. How would the electrical conductivity of the metals above change with increasing temperature? How would the electrical conductivity of silicon compare with the metals above. How would the conductivity of Si change with increasing temperature? 3. Arrange the following 3,5‐semiconductors in order of increasing band gap energy. BN AlP GaAs InAs 4. The dicarborane C2B4H6 can be prepared by adding acetylene to arachno‐B4H10. Predict the structure of C2B4H6 using Wade’s rules. What is the point group symmetry of C2B4H6? 5. The cage structure of quartz is hydrophobic while the cage of feldspar is hydrophilic. Describe how quartz and feldspar are related and account for the difference in the way they interact in an aqueous environment. 6. The carbonyl ligand, CO, is able to stabilize metal atoms in unusually low oxidation states through “back bonding”. What metal and ligand orbitals interact in back bonding? 7. Consider the free aluminum atom. What is the degeneracy of the ground state term? What is the term symbol for the ground state, ignoring spin‐orbit coupling? What excited state terms result from the effects of interelectron repulsions? Show how the effects of spin‐orbit coupling break the degeneracy of the ground state. Give ground‐ and excited‐state terms. 8. What physical property can be associated with the Racah B parameter? How does Bfree ion compare with Bcomplex for a transition metal ion? 9. What is the orbital degeneracy of an F free ion term? How is this degeneracy broken in an octahedral crystal field? What symbols are associated with the resulting terms? 10. Describe how the crystal field parameter Dq is dependent on the charge of the complexed metal ion. How does Dq change for 2nd and 3rd row transition metal ions relative to first row metals? ...
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This note was uploaded on 11/16/2011 for the course CHEM 4011 at Colorado.