Identifying types of IMF’s – intermolecular forces
Identifying polar vs nonpolar:
*You MUST know the shape of the molecule! But when you draw dipoles, draw them on a normal
Lewis dot structure.
Overall shape of molecule
Tetrahedral (CH4, CCl4)
# Identical polar covalent bonds
All 4 bonds are alike
Polar or nonpolar?
Nonpolar
Tetrahedral (CHCl3, CHCl2)
At least 1 bond is different
polar
Trigonal pyramidal (NH3, NCl3)
Bonds all alike OR different
Always polar
Bent (H2O)
Bonds all alike OR different
Always polar
Trigonal planar (AlH3, BF3)
All3 bonds alike
Nonpolar
Trigonal planar (AlHCl2)
At least 1 bond is different
Polar
Linear (O=C=O)
All bonds the same
Nonpolar
Linear (S=C=O)
All bonds different
polar
Remember the forces: (listed in order of increasing strength)
1. Van der waal’s (London dispersion)  Nonpolar covalent bonds
a. increase with increased numbers of molecules (increased molecular weight)
b. increase with long straight chains instead of branched molecules
2. Dipole interactions  Polar covalent bonds
3. Hydrogen bonding  H: O, N, F
4. Ionic  Metal : Nonmetal
*the stronger the IMF 
a. greater surface tension
b. higher melting point
c. higher the boiling point
d. more likely to be solid at RT
 notice C, D, and E kind of go together.
e. LESS likely to evaporate
Question: In what state at room temperature is each of the group 7 elements? What type of force causes
this change?