1. Intermolecular Forces

2. Types of bonds Ionic – transfer of e- from one atom to another
Covalent - sharing of e- between atoms
a) nonpolar covalent – equal sharing of e-
b) polar covalent – unequal sharing of e-

3. Polar bonds and Electronegativity
Electronegativity is the ability of an atom to attract electrons in a chemical bond
Polar bonds result when a highly electronegative atom bonds to a less electronegative atom

4. Write the formula, draw, and determine the Polarity of the following molecules:
Water
Carbon tetrachloride
Carbon monoxide
Carbon dioxide
Ammonia (NH3)
Methyl chloride (CH3Cl)
Sulfur dioxide
Boron trichloride
ICl4-

5. Intermolecular forces – the attractions between molecules
Determine whether a compound is a solid, liquid or gas at a given temperature (determine melting and boiling points of substances)
3 Main Types:
a) Hydrogen bonding (strongest)
b) Dipole-dipole interactions
c) Dispersion forces (weakest)

6. Hydrogen Bonding
Attraction formed between the hydrogen atom of one molecule and an electronegative atom of an adjacent molecule (O, N, or F)
A type of dipole interaction and the strongest intermolecular force
Examples: H2O, HF, NH3

7. Dipole-dipole interactions
Dipoles interact by the positive end of one molecule being attracted to the negative end of another molecule (similar to but much weaker than ionic bonds)
Occur between polar molecules
Examples: HBr, PH3, H2S

8. Dispersion Forces (Van der Waals)
Caused by electron motion. Electrons around one molecule momentarily repel electrons a nearby molecule creating a momentary charge difference
Occurs between nonpolar molecules
Weakest intermolecular force but increases as the number of electrons increases

9. Intermolecular forces and melting/boiling point

10. Van der Waals/London Dispersion
Types of Forces
Van der Waals/London Dispersion
Dipole-dipole
Hydrogen bonds
Strength
Increase strength of forces as electron number increases
Mimic ionic compounds (attracted by charges, but weaker)
Strongest (includes all 3 forces)
Types of Molecules
Any covalent compound with electrons (non-polar)
A force between 2 polar molecules
Force between 2 very polar, hydrogen containing molecules
Description of force
More electrons=stronger the force
Positive atom on one molecule attracts the negative atom of another molecule
Created with O, F, & N ONLY
Examples
Diatomic elements:
Br I N Cl H O F
CH3COCH3
H2O where H of one water is attracted to the O of another water