6.3 Intermolecular forces

• Intermolecular forces are weak attractions that exist between molecules
• Types of intermolecular force

  • induced dipole-dipole interactions
  • permanent dipole-dipole interactions
  • hydrogen bonds
• Induced dipole-dipole interaction is the attraction between two induced dipoles, where one molecule induces an instantaneous dipole on another molecule.
• Hydrogen bonding is the strongest type of intermolecular force, which occurs when hydrogen atoms covalently bonded to highly electronegative elements (F, O or N) form partial positive charge. This partial positive charge then forms strong electrostatic attractions with lone pairs of electrons on other highly electronegative atoms.
• Permanent dipole-dipole interaction is the attraction between permanent dipoles, where there is no change to either molecule but they attract due to their opposite charges.
• More electrons leads to stronger induced dipole-dipole interactions
• The more polar a substance is, the greater its ability to interact through induced dipole-dipole interactions