Intermolecular forces

• What are intermolecular forces?

  Interactions between molecules caused by dipoles
• What do intermolecular forces hold together?

  Simple covalent molecules
• What are London forces also known as?

  Van der Waals forces
• What causes the formation of an instantaneous dipole?

  Random movement of electrons within shells
• How does the number of electrons affect London forces?

  More electrons increase the strength of London forces
• What shape of a molecule has greater London forces?

  Molecule with the greatest surface area
• What is a hydrogen bond?

  Attraction between electron-deficient hydrogen and lone pairs
• Which atoms can form hydrogen bonds?

  Oxygen, nitrogen, and fluorine
• Why can water molecules form hydrogen bonds?

  They contain oxygen, which is electronegative
• How do hydrogen bonds compare to covalent bonds?

  Hydrogen bonds are weaker than covalent bonds
• What type of molecules have permanent dipoles?

  Polar molecules like HCl
• What causes the attraction in dipole-dipole interactions?

  Oppositely charged ends of polar molecules
• How does electronegativity affect dipole strength?

  Greater difference increases dipole strength
• Can hydrogen atoms attached to carbon form hydrogen bonds?

  No, they cannot form hydrogen bonds
• Why can't hydrogen atoms attached to carbon form hydrogen bonds?

  Electronegativities of carbon and hydrogen are similar
• What should be included when drawing hydrogen bonds between molecules?

  • Dipole changes on relevant atoms
  • Lone pairs of electrons on O, N, or F
  • Indicate hydrogen bond with a dashed line
  • OHO bond angle should be 180°
• Where can you find more information on electronegativity?

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