Содержание
- 2. The Shapes of Molecules 10.1 Depicting Molecules and Ions with Lewis Structures 10.2 Using Lewis Structures
- 3. On the Value of Lewis Structures A Lewis structure is a two-dimensional (2D) representation of a
- 4. Figure 10.1 Steps to convert a molecular formula into a Lewis structure Molecular formula Atom placement
- 5. Molecular formula Atom placement Sum of valence e- Remaining valence e- Lewis structure For NF3 N
- 6. SAMPLE PROBLEM 10.1 Writing Lewis Structures for Molecules with One Central Atom SOLUTION: Step 1: Carbon
- 7. SAMPLE PROBLEM 10.2 Writing Lewis Structures for Molecules with More than One Central Atom SOLUTION: Hydrogen
- 8. Lewis Structures for Molecules with Multiple Bonds After applying Steps 1-4, there may not be enough
- 9. SAMPLE PROBLEM 10.3 Writing Lewis Structures for Molecules with Multiple Bonds PLAN: SOLUTION: PROBLEM: Write Lewis
- 10. Resonance: Delocalized Electron-Pair Bonding Resonance structures have the same relative placement of atoms but different locations
- 11. Resonance structures are not real bonding depictions. The actual molecule is a resonance hybrid, an average
- 12. SAMPLE PROBLEM 10.4 Writing Resonance Structures PLAN: SOLUTION: PROBLEM: Write resonance structures for the nitrate anion,
- 13. When two or more unsymmetrical resonance forms exist: How do you determine which form exerts the
- 14. Formal Charge: Selecting the Best Resonance Structure An atom “owns” all of its non-bonding electrons and
- 15. Resonance (continued) Smaller formal charges (either positive or negative) are preferable to larger formal charges. Avoid
- 16. EXAMPLE: NCO- has three possible resonance forms. Resonance (continued) Formal charges: -2 0 +1 -1 0
- 17. Lewis Structures for Exceptions to the Octet Rule (a) Electron-Deficient Molecules: gaseous molecules containing either Be
- 18. SAMPLE PROBLEM 10.5 Writing Lewis Structures for Exceptions to the Octet Rule PLAN: SOLUTION: Draw the
- 19. Heats of Reactions from Lewis Structures and Bond Energies (1) Break all bonds found in the
- 20. Figure 10.2 Using bond energies to calculate ∆H orxn ΔHorxn = ΔHoreactant bonds broken + ΔHoproduct
- 21. Figure 10.3 Using bond energies to calculate ΔH orxn of methane combustion Enthalpy,H BOND BREAKAGE 4
- 22. SAMPLE PROBLEM 10.6 Calculating Enthalpy Changes from Bond Energies SOLUTION: bonds broken bonds formed
- 23. SAMPLE PROBLEM 10.6 (continued) bonds broken bonds formed 4 C-H = 4 mol (413 kJ/mol) =
- 24. Valence-shell Electron-Pair Repulsion (VSEPR) Theory A method to predict the shapes of molecules from their electronic
- 25. Figure 10.4 A balloon analogy for the mutual repulsion of electron groups
- 26. Figure 10.5 Electron-group repulsions and the five basic molecular shapes Ideal bond angles are shown for
- 27. Figure 10.6 The single molecular shape of the linear electron-group arrangement Examples: CS2, HCN, BeF2
- 28. Figure 10.7 The two molecular shapes of the trigonal planar electron-group arrangement Examples: SO3, BF3, NO3-,
- 29. Factors Affecting Actual Bond Angles Observed bond angles are consistent with theoretical angles when (a) the
- 30. Figure 10.8 The three molecular shapes of the tetrahedral electron-group arrangement Examples: CH4, SiCl4, SO42-, ClO4-
- 31. Figure 10.9 Lewis structures and molecular shapes
- 32. Figure 10.10 The four molecular shapes of the trigonal bipyramidal electron-group arrangement Examples: SF4 XeO2F2 IF4+
- 33. General trend for electron-pair repulsions for similar molecules with a given electron-group arrangement: Lone pair -
- 34. Figure 10.11 The three molecular shapes of the octahedral electron-group arrangement Examples: SF6 IOF5 Examples: BrF5
- 35. Figure 10.12 The steps in determining a molecular shape Molecular formula Lewis structure Electron-group arrangement Bond
- 36. SAMPLE PROBLEM 10.7 Predicting Molecular Shapes with Two, Three, or Four Electron Groups The shape is
- 37. SAMPLE PROBLEM 10.7 (continued) (b) For COCl2, C has the lowest EN and will be the
- 38. SAMPLE PROBLEM 10.8 Predicting Molecular Shapes with Five or Six Electron Groups (b) BrF5 - 42
- 39. Molecular Shapes With More Than One Central Atom Combinations of the molecular shapes observed when a
- 40. Figure 10.13 The tetrahedral centers of ethane
- 41. Figure 10.13 The tetrahedral centers of ethanol
- 42. SAMPLE PROBLEM 10.9 Predicting Molecular Shapes with More Than One Central Atom SOLUTION:
- 43. Molecular Polarity Both shape and bond polarity determine molecular polarity. Dipole moment (μ) = the product
- 44. Figure 10.14 The orientation of polar molecules in an electric field
- 45. SAMPLE PROBLEM 10.10 Predicting the Polarity of Molecules (a) ammonia, NH3 (b) boron trifluoride, BF3 (c)
- 46. SAMPLE PROBLEM 10.10 (continued) (b) BF3 has 24 valence electrons and all electrons around the B
- 47. The Complementary Shapes of an Enzyme and Its Substrate
- 48. Biological Receptors: Olfactory Biochemistry
- 49. Shapes of Some Olfactory Receptor Sites Three of the proposed seven olfactory receptors having different shapes
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