Liquids

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Intermolecular Forces

• Liquids

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A. Definition of IMF

• Attractive forces between molecules.

• Much weaker than chemical bonds within
  molecules.

• van der Waals forces

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Intermolecular Forces of Attraction (IMF)

• Dipole-dipole Forces
• Ion- Dipole Forces
• Ion/Dipole-Induced Dipole
• Dispersion Forces
• Hydrogen Bonding

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Dipole-Dipole Forces

• Attractive forces between polar molecules
  (molecules with large EN difference, thus have
  dipole moments)

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Ion-Dipole Forces

• Attraction between an ion (anion / cation) a
  polar molecule to each other.

cation polar molecule
anion polar molecule
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Ion-Induced Dipole Dipole Induced Dipole

• Induced Dipole- due to the separation of positive
  negative charges in an atom (or a non-polar
  molecule) caused by the proximity of an ion or a
  polar molecule.

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ion non-polar molecule
Induced dipole
polar non-polar molecule
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Dispersion Forces

• Attractive forces that arise as a result of
  temporary dipoles induced in atoms or molecules
• Exists in all types of species (neutral, charged,
  polar, non-polar)

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Hydrogen Bonding

• Special type of dipole-dipole interaction between
  Hydrogen atom in a polar bond, such as N-H, O-H
  or F-H an electronegative O, N, or F atom.

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Exercises

• What type of intermolecular forces exist between
  the following?
• (a) HBr HCl
• (b) Cl2 CBr4
• (c) I2 NO3-
• (d) NH3 C6H6

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Exercises

• Which of the following can form hydrogen bonds
  with water?
• (a) CH3OCH3
• (b) CH4
• (c) F-
• (d) HCOOH
• (e) Na