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6.5

6.5. Molecular Geometry. 6.5 NOTES. The properties (solubility, state at room temperature, etc.) of a molecule depend on two things :. 6.5 NOTES. The properties of a molecule depend on two things: The type(s) of atoms involved. The shape of the molecule. 6.5 NOTES.

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6.5

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  1. 6.5 Molecular Geometry

  2. 6.5 NOTES The properties (solubility, state at room temperature, etc.) of a molecule depend on two things:

  3. 6.5 NOTES The properties of a molecule depend on two things: • The type(s) of atoms involved. • The shape of the molecule.

  4. 6.5 NOTES The properties of a molecule depend on two things: • The type(s) of atoms involved. • The shape of the molecule. What is VSEPR?

  5. 6.5 NOTES The properties of a molecule depend on two things: • The type(s) of atoms involved. • The shape of the molecule. Valence Shell Electron Pair Repulsion = VSEPR

  6. 6.5 NOTES The properties of a molecule depend on two things: • The type(s) of atoms involved. • The shape of the molecule. Valence Shell Electron Pair Repulsion = VSEPR Valence electron pairs tend to orient themselves as far apart from each other as possible. This applies to bonded and unbonded pairs, however, unbonded pairs tend to have more of an affect than bonded pairs. Why?

  7. 6.5 NOTES The properties of a molecule depend on two things: • The type(s) of atoms involved. • The shape of the molecule. Valence Shell Electron Pair Repulsion = VSEPR Valence electron pairs tend to orient themselves as far apart from each other as possible. This applies to bonded and unbonded pairs, however, unbonded pairs tend to have more of an affect than bonded pairs. Unbonded pairs are held closer in to the molecule, so they exert more influence on the shape of the molecule.

  8. 6.5 NOTES The properties of a molecule depend on two things: • The type(s) of atoms involved (polar or nonpolar bonds). • The shape of the molecule. Valence Shell Electron Pair Repulsion = VSEPR A = central atom B = other atoms bonded to the central atom E = unbonded electron pairs on the central atom

  9. 6.5 NOTES LOOKING AT THE SHAPES: • http://phet.colorado.edu/en/simulation/molecule-shapes

  10. is a bonded atom is the center atom are unbonded electrons Remember: unbonded electrons exert much more influence on the shape of the molecule

  11. 6.5 NOTES p. 200 – Memorize name, shape, and type of molecule

  12. 6.5 NOTES Hybridization explains exactly where the electrons are positioned. (s, px,py,pz, etc.) It helps account for the electrons being spread around the entire molecule. If an “s” electron pairs with a “p” electron, it is called an “sp” orbital. P. 203

  13. 6.5 NOTES Hybridization explains exactly where the electrons are positioned. (s, px,py,pz, etc.) It helps account for the electrons being spread around the entire molecule.

  14. 6.5 NOTES Hybridization explains exactly where the electrons are positioned. (s, px,py,pz, etc.) It helps account for the electrons being spread around the entire molecule.

  15. 6.5 NOTES Hybridization explains exactly where the electrons are positioned. (s, px,py,pz, etc.) It helps account for the electrons being spread around the entire molecule. If an “s” electron pairs with a “p” electron, it is called an “sp” orbital. p. 203 In CH4 the s and p orbitals actually form “sp” hybrid orbitals for the electrons to occupy.

  16. 6.5 NOTES In double bonds, the electrons repel each other so they spread out the bond area. A sigma (σ) bond is between the nuclei of the two atoms. A pi (π) bond is above and below the sigma bond.

  17. 6.5 NOTES Let’s determine some molecules shapes and polarity: OF2

  18. 6.5 NOTES Let’s determine some molecules shapes and polarity: CO2

  19. 6.5 NOTES Let’s determine some molecules shapes and polarity: HCN

  20. 6.5 NOTES Let’s determine some molecules shapes and polarity: CH4

  21. 6.5 NOTES Let’s determine some molecules shapes and polarity: NH3

  22. 6.5 NOTES Let’s determine some molecules shapes and polarity: BCl3 (B is an exception, because of its size it can only accommodate 6 electrons to be stable)

  23. 6.5 NOTES Let’s determine some molecules shapes and polarity: SO2

  24. 6.5 NOTES What is the shape of these polyatomic ions? NO31-

  25. 6.5 NOTES What is the shape of these polyatomic ions? NH41+

  26. 6.5 NOTES So why is a molecule’s shape and the type of bonds it contains important?

  27. 6.5 NOTES So why is a molecule’s shape and the type of bonds it contains important? That is what will determine: • the state of matter for the molecule • the melting and boiling points • the ability to dissolve in water

  28. 6.5 NOTES What are intermolecular forces?

  29. 6.5 NOTES Intermolecular forces exist between one molecule and another molecule. Also called van der Waals forces They are weaker than intramolecular forces (covalent bonds).

  30. 6.5 NOTES Intermolecular forces exist between one molecule and another molecule. What are the 3 types?

  31. 6.5 NOTES Intermolecular forces exist between one molecule and another molecule. 3 types • London dispersion forces (p. 207) weakest occurs between 2 nonpolarmolecules

  32. 6.5 NOTES Intermolecular forces exist between one molecule and another molecule. 3 types • London dispersion forces (p. 207) weakest occurs between 2 nonpolarmolecules occurs for a short time when the electrons, which are constantly moving in a molecule, are not completely balanced (one side is temporarily negative and the other side is temporarily positive). this temporary charge then induces another molecule to have a temporary positive or negative end.

  33. 6.5 NOTES Intermolecular forces exist between one molecule and another molecule. 3 types • London dispersion forces (p. 207) weakest occurs between 2 nonpolar molecules (usually large molecules) occurs for a short time when the electrons, which are constantly moving in a molecule are not completely balanced (one side is temporarily negative and the other side is temporarily positive). this temporary charge then induces another molecule to have a temporary positive or negative end. also called induced dipole

  34. 6.5 NOTES Intermolecular forces exist between one molecule and another molecule. 3 types • London dispersion forces • Hydrogen bonding (p. 206) the next strongest of the forces The hydrogen atom of one molecule is attracted to the nitrogen, oxygen, or fluorine in another molecule. All the atoms have to be in polar bonds.

  35. 6.5 NOTES Intermolecular forces exist between one molecule and another molecule. 3 types • London dispersion forces • Hydrogen bonding • Dipole-dipole forces (p. 205-206) strongest of the intermolecular forces Occurs between two polar molecules Partial positive end of one is attracted to partial negative end of another.

  36. A technician was cleaning up the laboratory when he discovered two steel gas cylinders. Puzzled as to what was inside, the technician took the cylinders to his supervisor.

  37. A technician was cleaning up the laboratory when he discovered two steel gas cylinders. Puzzled as to what was inside, the technician took the cylinders to his supervisor. “One contains gaseous F2 and the other Cl2, said his supervisor. “But which is which?” asked the technician. The supervisor responded indignantly, that to a chemist, the answer should be obvious.

  38. A technician was cleaning up the laboratory when he discovered two steel gas cylinders. Puzzled as to what was inside, the technician took the cylinders to his supervisor. “One contains gaseous F2 and the other Cl2, said his supervisor. “But which is which?” asked the technician. The supervisor responded indignantly, that to a chemist, the answer should be obvious. Which tank is which?

  39. HINTS: • Which intermolecular force is present in • these tanks?

  40. HINTS: • Which intermolecular force is present in • these tanks? • How would molecule size affect this • force?

  41. HINTS: • Which intermolecular force is present in • these tanks? • How would molecule size affect this • force? • Do stronger forces result in a higher or • lower boiling point?

  42. HINTS: • Which intermolecular force is present in • these tanks? • How would molecule size affect this • force? • Do stronger forces result in a higher or • lower boiling point? • Which substance has the stronger • intermolecular forces?

  43. Which tank contains which gas?

  44. CHAPTER 6 TEST • 25 multiple choice (3 points each) • 5 drawing molecules (5 points each) • 1 extra credit (3 points)

  45. CHAPTER 6 TEST • 3 types of bonding • Covalent • Ionic • Metallic • Chart p. 176 • 0 – 0.4 = nonpolar covalent • 0.5 – 1.9 = polar covalent • 2.0 and above = ionic • Properties of ionic and covalent compounds • Bond length vs bond energy • Octet rule (there are exceptions – B, Be, H, S, and P are the common ones)

  46. CHAPTER 6 TEST • Electron dot notation for atoms and ions • Lewis structures for covalent compounds • Resonance structures • Lattice energy • Polyatomic ions – how to draw them (remember to add or subtract e-) • Using VSEPR to determine shapes • Chart p. 200 • Intermolecular forces • London Dispersion forces • Hydrogen bonding • Dipole-dipole bonding • Hybridization

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