Dipole Moments

Question 1

Define dipole moments

Answer 1

When atoms in a molecule share electrons unequally.
Atoms with a big difference in electronegativity

occurs when:
- One atom is more electronegative than the other, resulting in the atom pulling more tightly on the shared pair of electrons
- One atom has a lone pair of electrons and the difference of electronegativity vector points in the same way

Question 2

Define bond polarity

Answer 2

• Shape of molecule and the polarity of its bonds determine overall polarity of that molecule
• Some might not have any overall polarity, depending on its shape
• Bond dipoles can cancel each other out (symmetry)

Question 3

Describe the 3 types of Van der Waals forces.

Answer 3

1. Hydrogen bonding
   - Hydrogen bonded to a very small, very EN atom (N, O, F)
   - Strongest of intermolecular forces
2. Permanent dipole - permanent dipole (pd-pd)
   - Between polar molecules
   - 2nd strongest
3. Instantaneous dipole - induced dipole (id-id)
   - Between non-polar molecules
   - Weakest
   - Also known as London Dispersion forces
   - The greater the number of electrons, the stronger the London Dispersion forces will be