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3 January 2012

3 January 2012. Take Out Bonding Problem Set Objective : You will be able to: describe the VSEPR model and describe molecular geometry for 2 to 4 electron domains Do now: On your white paper, across the top of a long edge, draw the Lewis structures for: carbon dioxide boron trifluoride

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3 January 2012

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  1. 3 January 2012 • Take Out Bonding Problem Set • Objective: You will be able to: • describe the VSEPR model and describe molecular geometry for 2 to 4 electron domains Do now: On your white paper, across the top of a long edge, draw the Lewis structures for: • carbon dioxide • boron trifluoride • methane • ammonia

  2. Agenda • Homework Quiz • Collect Winter Break Homework • We’ll do a review of intermolecular forces after this current (short) unit • VSEPR Theory and Molecular Geometry Homework: p. 453 #1, 2, 7, 9, 12 (please sketch neatly!): tomorrow I’ll collect the Intermolecular Forces problem set tomorrow. See me after school with questions!

  3. Keys?

  4. The VSEPR Model • Valence-shell electron-pair repulsion (VSEPR) model: a way to use Lewis structures to determine the geometries (shapes) of molecules. • based on repulsive forces that exist between electron pairs within molecules • geometry: the arrangement of a molecule’s atoms in three-dimensional space

  5. bond angle: an angle made by the lines joining the nuclei of atoms in a molecule • electron domain: a region around an atom in which electrons will most likely be found. • produced by a non-bonding pair, a single bond, a double bond or a triple bond

  6. Activity • On your white paper, across the top of a long edge, draw the Lewis structures for: • carbon dioxide • boron trifluoride • methane • ammonia • Then, with your knowledge of the VSEPR theory, construct models for each molecule that predict it’s 3D geometry. Sketch these below each Lewis structure. • Measure and label the bond angles.

  7. Linear2 bonding domains0 non-bonding domains180o

  8. Trigonal Planar3 bonding domains0 non-bonding domains120o

  9. Non-linear (bent)2 bonding domains1 non-bonding domain117o

  10. Tetrahedral4 bonding domains0 non-bonding domains109.5o

  11. Trigonal pyramidal3 bonding domains1 non-bonding domain107o

  12. Non-linear (bent)2 bonding domains2 non-bonding domains104o

  13. On your paper • Label the shapes of the four molecules you already constructed • Draw Lewis structures for • NO2- • H2O • Determine their shape. Build the model. • Draw a sketch, label the shape name and the bond angle.

  14. Next Up • What about molecules with 5 or 6 electron domains?!

  15. Homework • p. 453 #1, 2, 7, 9, 12: tomorrow

  16. 4 January 2012 • Take Out: Problem sets, p. 453 Homework • Objective: You will be able to: • use VSEPR theory to determine the shapes of molecules with five and six electron domains around the central atom. • Homework Quiz: Draw the Lewis structure, determine the shape, sketch, label the bond angle: HCF3 • Bonus: Describe the polarity of this molecule.

  17. Agenda • Homework Quiz • Homework Answers • Shapes of molecules with five and six electron domains: Notes • Polarity? • Homework: p. 453 #7d, 8, 10, 12d, e, g, 13, 14: Mon. • read p. 420-423, ignore equations: Mon.

  18. Draw Lewis Structures for… • PCl5 • SF4 • ClF3 • XeF2

  19. Electron-Domain Geometry • Trigonalbipyramidal: 5 electron domains • trigonalbipyramidal (5 bonding, 0 non) • seesaw (4, 1) • T-shaped (3, 2) • Linear (2, 3)

  20. Draw Lewis Structures for… • SF6 • BrF5 • XeF4

  21. Electron-Domain Geometry • Octahedral: 6 electron domains • octahedral (6 bonding, 0 non) • square pyramidal (5, 1) • square planar (4, 2)

  22. 9 January 2012 • Take Out Homework • Objective: You will be able to: • identify and describe the polarity of bonds and molecules • Homework Quiz: a. Draw a Lewis Structure b. Identify the shape c. Sketch • a. IBr3 b. SI6

  23. Agenda • Homework Quiz • Homework Answers • Polarity Notes and Practice Problems • Hand back assignments Homework: p. 454 #18, 20, 23 finish polarity practice problems read p. 428-436

  24. Practice Problems • Draw Lewis Structures, predict geometry (electron domain and molecular), sketch, label: • PBr5 • SI6 • ClF4+ • SF5- • BCl3 • IBr3 • XeCl2

  25. Polarity • bond polarity: a measure of how equally the electrons in a bond are shared between two atoms. • the greater the difference in electronegativity of the bonded atoms, the more polar the bond.

  26. dipole moment: measure of the charge separation in a molecule; how polar the entire molecule is • the vector sum of all the bond dipoles

  27. Examples • HCl • BF3 • CCl4 • NH3 • CH3Cl

  28. Examples • C2H2Cl2

  29. Practice Problems • 1. SO2 9. BF3 • 2. CCl4 10. SF3+ • 3. CHCl3 11. XeF2 • 4. TeCl2 12. BrF5 • 5. CO32- 13. XeF4 • 6. NH3 14. SeF4 • 7. SO42- 15. ClF3 • 8. CO2 16. SeF6

  30. Homework • p. 454 #18, 20, 23 • finish polarity practice problems • read p. 428-436

  31. 10 January 2012 • Take Out Homework • Objective: You will be able to: • describe and identify hybridization of orbitals in molecules and describe and count sigma and pi bonds. • Homework Quiz: SF3+a. Draw the shape and label with the shape name. b. Indicate bond moments. c. Indicate dipole moment, if any. d. Polar or non polar?

  32. Agenda • Homework Quiz • Hybridization Notes and Practice Problems • Sigma and Pi Bond Notes and Practice Problems Homework: p. 454 #31, 32, 34, 35, 37, 39, 40, 41, 42, 69, 71, 75, 82, 99 b0nus: 100: Thurs.

  33. Hybridization

  34. VSEPR Theory Review • Valence electrons only are involved in bonding. • Non-bonding and bonding electron pairs around the central atom repel each other. • This repulsion causes specific shapes and bond angles for each molecule.

  35. Question • How can atoms, that have s, p and d orbitals, bond in ways that make the molecule shapes? • Ex: p orbitals at 90o angles to each other. • How can they make a bond angle of 109.5o in tetrahedral or 120o in trigonal planar?? ?

  36. Energy 1s 2s 2p 1s Carbon Hydrogen How can carbon make four bonds with four hydrogen atoms?? How can those bonds be at 109.5o (tetrahedral)?

  37. Answer: Hybrid orbitals: the sublevels in an atom’s outer shell recombine into new orbitals of equal energy with different shapes and angles. Energy 1s sp3 hybrid orbital • Hybridization: the mixing of atomic orbitals in an atom (usually the central atom) to generate a set of hybrid orbitals.

  38. Energy • Total energy the same, but redistributed 1s 2s 2p 1s Carbon Hydrogen Energy 1s sp3 hybrid orbital 39

  39. Animation • http://www.youtube.com/watch?v=g1fGXDRxS6k • http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/hybrv18.swf

  40. sp3 Example • CH4

  41. sp hybridization • BeCl2

  42. 12 January 2012 • Objective: You will be able to: • describe and identify hybridization of orbitals in molecules and describe and count sigma and pi bonds. • review bonding and molecular geometry.

  43. Agenda • Hybridization notes • Practice problems • Sigma and pi bond notes and examples • Problem Set work time Homework: p. 454 #31, 32, 34, 35, 37, 39, 40, 41, 42, 69, 71, 75, 82, 99 b0nus: 100: Tues. Problem Set: Tues Test Weds.

  44. sp2 hybridization • BF3

  45. Shapes of hybrid orbitals s, p s, p, p trigonal pyramidal s, p, p, p

  46. NH3 is also sp3 hybridization: three orbitals for the H, one orbital for the non-bonding pair.

  47. Steps to Determine Hybridization • Draw the Lewis structure • Predict the molecule shape using the VSEPR theory • Determine hybridization by matching the arrangement of the molecule with known examples (table 10.4)

  48. For each compound’s central atom, draw the orbital notation. • Then, draw the orbital notation after hybridization. • Name the type of hybridization and the shape of each molecule. • BeH2 • AlI3 • PF3 • SiF4 • CO2 • PH3 • H2O

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