Intermolecular Forces

• How are London dispersion forces and D.D.I. different?

  D.D.I. is between polar molecules , London dispersion between nonpolar molecules and neutral atoms.
• How are London dispersion forces and D.D.I. similar?

  Both have partial charges
• What causes a London dispersion force to occur between two atoms or molecules?

  Constant motion of electrons creating momentary dipoles.
• What helps neutral atoms and molecules attract each other?

  Momentary dipoles
• Hydrogen and covalent bond difference

  Hydrogen bond= intermolecular; covalent bond= intramolecular
• Hydrogen and covalent bond similarity

  Forces of attraction holding something together.
• Is a hydrogen bond the same as a covalent bond?

  No, hydrogen is between molecules whole covalent bonds hold molecules together.
• What causes the dipole in polar covalent molecules?

  The difference in electronegativity. The atom with higher electronegativity has stronger attraction.
• Dipole


  Opposite charges separated by a short distance.
• Intramolecular / intermolecular forces are attractions between molecules.


  Intermolecular
• Intramolecular / intermolecular forces hold the molecule together.


  Intramolecular
• Hydrogen bonding


  Type of dipole - dipole interaction that occurs only in molecules that contain O-H, N-H, or F-H bonds. O, N, and F are highly electronegative and have highly localized -ve charge. H has only 1 proton and highly localized +ve charge. Electrostatic attraction is higher when compared to other polar molecules. Stronger than D.D.I.
• Dipole - dipole interaction- involves polar or nonpolar molecules?

  Polar
• Dipole - dipole interaction

  Interaction between 2 net dipoles of same molecules. Stronger than dispersion forces. Partial positive charge on one molecule attracts the positive negative charge of another.
• Dispersion forces- involves polar or nonpolar molecules?

  Nonpolar
• Dispersion forces

  Between molecules due to attraction of electrons to nuclei of other molecules or due to momentary dipoles when molecules approach each other. Increases with increase of # of electrons in a molecule.
• Strength of intermolecular forces, weakest ---> strongest

  Dispersion forces < dipole - dipole interaction < hydrogen bonding
• 3 types of intermolecular forces:

  London dispersion forces, dipole - dipole interaction, hydrogen bonding
• Intermolecular forces


  Forces that operate between covalent molecules