10 - CHEMISTRY 121 Problem Set 10 answers 1 Valence Bond Theory 1 Give the hybridization of the central atom(atoms in the case of e and f in each

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CHEMISTRY 121 1 Department of Chemistry University of British Columbia Problem Set 10 answers Valence Bond Theory 1. Give the hybridization of the central atom (atoms in the case of e and f) in each of the following molecules or ions. (a) CF 4 The answer is: sp 3 . Four electron pairs on C sp 3 (b) [PCl 6 ] The answer is: sp 3 d 2 . Six electron pairs on P sp 3 d 2 (c) [SiCl 5 ] The answer is: sp 3 d . Five electron pairs on Si sp 3 d (d) BBr 3 The answer is: sp 2 . Three electron pairs on B sp 2 (e) C 2 F 4 The answer is: sp 2 on both carbons . Three electron pairs on each C (by VSEPR counting) sp 2
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CHEMISTRY 121 2 Department of Chemistry University of British Columbia Note: the singly occupied p orbitals on each C will overlap to form a π bond, thus completing the double bond in the structure. (f) C 2 Cl 2 The answer is: sp on both carbons . Two electron pairs on each C (by VSEPR counting) sp Note: the two singly occupied p orbitals on each C will overlap to form two π bonds, thus completing the triple bond in the structure. 2. Consider each of the following species to answer parts a – d. SiH 4 , NCCN, SF 6 , SeF 4 , PH 3 (a) Which are polar molecules? The answer is: SeF 4 and PH 3 (b) Which are linear molecules? The answer is: NCCN (c) Which molecules use sp 3 d 2 hybrid orbitals on the central atom for bonding? The answer is: SF 6 (d) Which molecules use sp 3 hybrid orbitals on the central atom for bonding? The answer is: SiH 4 and PH 3 For PH 3 , in the absence of experimental data we would predict P to be sp 3 hybridized. However, in light of the observed H-P-H bond angles (90°) many chemists believe that P is not hybridized and that the P-H bonds are formed through orthogonal 3 p orbitals on phosphorus and that the lone pair is in the 3 s orbital.
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CHEMISTRY 121 3 Department of Chemistry University of British Columbia Si H H H H S F F F nonpolar tetrahedral sp 3 for Si N CC N nonpolar linear sp for each C F F F Se F F F F nonpolar octahedral sp 3 d 2 for S polar see-saw sp 3 d for Se P H H H polar trigonal pyramidal sp 3 for P 3. If z is the internuclear axis between two atoms, list all the possible combinations of atomic orbitals ( s, p x , p y , p z d xy , d xz , d yz , d x 2 -y 2 , d z 2 ) on different atoms that can overlap to produce a σ bond?
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This note was uploaded on 11/03/2009 for the course ECON 210 taught by Professor James during the Spring '09 term at The University of British Columbia.

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10 - CHEMISTRY 121 Problem Set 10 answers 1 Valence Bond Theory 1 Give the hybridization of the central atom(atoms in the case of e and f in each

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