Welcome to Chem 1C with Terri Bentzinger E-mail: [email protected] Website: http://clas.sa.ucsb.edu/staff/terri/ Drop-in: M/T/W/R 1-2 pm ⇒ SRB Rm 3274 Bonding – ch. 13/14 Chem 1C is Very conceptual – lots of memorizing Bonding – ch. 13/14 1. Rank the following bonds in order of least polar to most polar: C-N C-O C-H C-Br Bonding – ch. 13/14 Bond Polarity ⇒ uneven distribution of bonding electrons due to a difference in electronegativity Red ⇒ high electron density Purple⇒ low electron density H⇒ 2.2 F⇒ 4.0 Bonding – ch. 13/14 2. For each of the following draw the Lewis structure, determine the electronic and molecular geometries, predict the bond angle, state if polar or non polar and label the hybridization on the central atom. a. BeF2 b. HCN c. SO2 d. PCl3 e. SF6 f. XeI5+ g. ICl4- Bonding – ch. 13/14 3. Place the following molecules in order from smallest to largest H−N−H bond angles: NH4+ NH3 NH2– Bonding – ch. 13/14 4. Rank the following in order of shortest to longest carbon-oxygen bond length: CO32- CO2 CO CH3OH Bonding – ch. 13/14 5. Which of the following shows these molecules in order from most polar to least polar? CH4 , CF2Cl2 , CF2H2 , CCl4 , CCl2H2 A) CH4 > CF2Cl2 > CF2H2 > CCl4 > CCl2H2 B) CH4 > CF2H2 > CF2Cl2 > CCl4 > CCl2H2 C) CF2Cl2 > CF2H2 > CCl2H2 > CH4 = CCl4 D) CF2H2 > CCl2H2 > CF2Cl2 > CH4 = CCl4 E) CF2Cl2 > CF2H2 > CCl4 > CCl2H2 > CH4 Bonding – ch. 13/14 6. For the following structures: a. Fill in the missing bonds/electrons (if any) b. Label the hybridization for the carbons, nitrogen and oxygen atoms c. Assign the indicated angles d. Determine the number of sigma (σ) and pi (π) bonds e. Describe the indicated bonds i j l m k Bonding – ch. 13/14 7. Which of the following resonance contributors for N2O is the most stable? Hint: calculate formal charges Bonding – ch. 13/14 8. Will all of the atoms in allene lie in the same plane? Bonding – ch. 13/14 9. Fill in the following table: Molecule/Ion H2 He2+ B2 CN– O2 Electron Configuration Bond Order Magnetism Bonding – ch. 13/14 Molecular orbitals S with S P with P Bonding – ch. 13/14 MO diagram for homonuclear molecules in Groups 1-5 MO diagram for homonuclear molecules in Groups 6-8 Bonding – ch. 13/14 σ2p* π2p* σ2p* π2p π2p* σ2p σ2p π2p σ2s* σ2s Alligators Like to eat Beef BaCoN Period 2, groups 1-5 σ2s* σ2s Hatchets chop OFf at the kNee Period 2, groups 6-8 Bonding – ch. 13/14 10. Label the following molecular orbitals. A. D. B. C. E. Bonding – ch. 13/14 11. Identify the element X if the ion X2- has the following valence electron configuration; (σ3s)2(σ3s*)2(π3p)4(σ3p)2(π3p*)1 Bonding – ch. 13/14 12. Using the MO model predict the relative bond dissociation energy for the following: F2 F2F 2+ Bonding – ch. 13/14 You have completed ch. 14 Bonding – ch. 13/14 – Answer Key 1. Rank the following bonds in order of least polar to most polar: C-N C-O C-H C-Br C-H < C-Br < C-N < C-O Bonding – ch. 13/14 – Answer Key 2. For each of the following draw the Lewis structure, determine the electronic and molecular geometries, predict the bond angle, state if polar or non polar and label the hybridization on the central atom. a. BeF2 => EG/MG-linear, 180º, non-polar, sp b. HCN => EG/MG-linear, 180º, polar, sp c. SO2 => EG-trigonal planar, MG-bent, 120º, polar, sp2 d. PCl3 => EG-tetrahedral, MG-trigonal pyramid, <109º, polar, sp3 e. SF6 => EG/MG-octahedral, 90º, non-polar, d2sp3 or sp3d2 f. XeI5+ => EG-octahedral, MG-square pyramid, 90º, polar, d2sp3 or sp3d2 g. ICl4- => EG-octahedral, MG-square planar, 90º, non-polar, d2sp3 or sp3d2 Bonding – ch. 13/14 – Answer Key 3. Place the following molecules in order from smallest to largest H−N−H bond angles: NH4+ NH3 NH2– NH2– < NH3 < NH4+ 4. Rank the following in order of shortest to longest carbon-oxygen bond length: CO32CO2 CO CH3OH CO < CO2 < CO32- < CH3OH 5. Which of the following shows these molecules in order from most polar to least polar? D) CF2H2 > CCl2H2 > CF2Cl2 > CH4 = CCl4 Bonding – ch. 13/14 – Answer Key 6. For the following structure: a. Fill in the missing bonds/electrons (if any) each nitrogen is missing 1 lone pair and each oxygen is missing 2 lone pairs b. Label the bonds as sigma (σ) or pi (π) single bonds are sigma, double bonds have one sigma and one pi, triple bonds have one sigma and two pi c. Label the hybridization for the carbons, nitrogens and oxygens. d. Assign the bond angles sp3 sp2 sp sp2 sp2 sp2 sp3 sp3 a. < 109.5° b. 120° c. <120° d. 120° e. 180° f. 120° g. <109.5° h. 109.5° Bonding – ch. 13/14 – Answer Key 7. Which of the following resonance contributors for N2O is the most stable? Hint: calculate formal charges F.C. = 5-3-2 = 0 F.C. = 5-2-4 = -1 F.C. = 5-4-0 = +1 F.C. = 6-2-4 = 0 F.C. = 5-1-6 = -2 F.C. = 5-4-0 = +1 F.C. = 6-1-6 = -1 F.C. = 5-4-0 = +1 F.C. = 6-3-2 = +1 Most stable ⇒ Minimum magnitude of F.C. and (-) F.C. on most EN atom Bonding – ch. 13/14 – Answer Key 8. Will all of the atoms in allene lie in the same plane? No Since pi is y then it’s sp2xz π can’t be x so let’s say y Since pi is z then it’s sp2xy if central C is spx all 3 Cs are on the x axis π can’t be x or y so z Bonding – ch. 13/14 – Answer Key 9. Molecule Electron Configuration Bond Order Magnetism H2 (σ1s)2 1 diamagnetic He2+ (σ1s)2(σ1s*)1 0.5 paramagnetic B2 (σ2s)2(σ2s*)2 0 paramagnetic CN- (σ2s)2(σ2s*)2(π2p)4(σ2p)2 3 diamagnetic O2 (σ2s)2(σ2s*)2(σ2p)2(π2p)4(π2p*)2 2 paramagnetic 10. a. σ1s* or σ2s* 11. P 12. F2+ > F2 > F2- b. σ2p c. π2p* d. σ1s or σ2s e. π2p

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