UNIT 10: LIQUIDS, SOLIDS & IMFs
INTERMOLECULAR FORCES (LONDON DISPERSION FORCES)
Intermolecular forces (IMFs): Keeps a molecule intact and keeps multiple molecules together
(noncovalent forces).
Intramolecular forces: The forces that hold atoms together in a molecule.
Kinetic energy (KE) provides the energy required to overcome the IMFs.
Types of Intermolecular Forces:
Dispersion Forces (London Dispersion Forces)
○ Present in ALL SUBSTANCES
○ Weakest type of intermolecular force;
○ Heavier molecules and atoms have stronger dispersion forces b/c their
valence electrons are farther from the nucleus (meaning it’s more
polarizable).
○ Polarizability: measure of the ability of a change to distort a molecule’s charge
distribution
○ Composed of instantaneous dipoles (constant motion of electrons and atoms)
and induced dipoles (distortion of neighboring atom/molecule)
○ Ex: noble gases (Argon), nonpolar molecules (CH4, CCl4 ).
2. Dipole-Dipole Attractions
○ Between polar molecules that have permanent dipoles. The positive end of one
molecule is attracted to the negative end of another.
○ Stronger than dispersion forces but weaker than hydrogen bonding.
○ Stronger dipole forces = increase in temperature
○ Examples: HCl, CH3Cl ,or SO2
3. Hydrogen Bonding
○ Donor: H atom bonded with N, O, or F
○ Acceptor: lone pair on N, O, or F
○ Strongest intermolecular force: tho weaker than covalent or ionic bonds.
○ Examples: Water (H2O), ammonia (NH3 ), and hydrogen fluoride (HF)
