Intermolecular Forces

• What are intermolecular forces?

  Forces between molecules
• What is the difference between intermolecular forces and covalent bonds?

  Intermolecular forces attract molecules, covalent bonds connect atoms
• Why are van der Waals forces considered weak?

  They arise from temporary dipoles
• What causes a temporary dipole in an atom?

  Uneven distribution of electrons
• How do temporary dipoles lead to attraction between molecules?

  Positive and negative ends attract each other
• What is a permanent dipole?

  A consistent positive and negative end in a molecule
• How do permanent dipoles attract each other?

  Positive end attracts negative end of another molecule
• What is an example of a molecule with a permanent dipole?

  Hydrogen chloride (HCl)
• What type of attraction occurs between molecules with permanent dipoles?

  Permanent dipole-dipole attraction
• What is a special case of permanent dipole-dipole attraction?

  Hydrogen bond
• When does a hydrogen bond occur?

  When hydrogen is bonded to fluorine, oxygen, or nitrogen
• How does the strength of hydrogen bonds compare to covalent bonds?

  Hydrogen bonds are weaker than covalent bonds
• What are the different types of intermolecular forces and their relative strengths?

  • Hydrogen bonds: strength ~10
  • Permanent dipole-dipole: strength ~5
  • Van der Waals forces: strength ~1
• What are the three types of bonding between molecules?

  Van der Waals, dipole-dipole, hydrogen bonds
• How does the strength of intermolecular bonds compare with a covalent bond?

  Intermolecular bonds are weaker than covalent bonds