Homework for tomorrow, Thursday, February 6th:
-2 Inter-molecular force worksheets
- One web assign due 11:59pm Wednesday night
REMINDER: Test Friday
All About Inter-Molecular Forces (IMF)
weakest 1)London Dispersion Forces (LDF) (aka Vanderwahl's force)
stronger 2) Dipole Dipole interaction
Strongest 3)Hydrogen bonding (n.b. misnomer - they are not officially bonds...)
1) LDF's---Between Non-polar molecules - weak and short lived
-Induced dipoles in a nonpolar molecule (temporary, billionths of a second)
- Although electrons are shared equally, they move constantly
- Electrons can flow more in one direction than another, creating a temporary dipole
- The larger/longer the nonpolar molecule, the larger the effect of LDFs, ie more viscous
e.g. Hydrocarbons---lots of bonds to create dipoles
2)Dipole-Dipole interactions - Between Polar Molecules - Stronger than LDFs
- Intrinsic (not induced)
-Permanent (not temporary)
- The attraction between positive (+) dipoles and negative (-) dipoles
3) Hydrogen bonding - DIPOLES ON STEROIDS - Really small and weak (and therefore negative) hydrogen bonded to either Fluorine, Oxygen, or Nitrogen
e.g. water (bent shape, polar) - Large, electronegative oxygen atom holds the electrons very close, thus forming a very negative dipole, while the hydrogen thus form very positive dipoles, attracting all the other extremely negative and positive dipoles of all the water around each other to 'stick' to each other - this stickiness is why water has such a high boiling point - 212 degrees Farenheit!
Sidenote: Bonds are giving and sharing electrons (ionic and covalent), while hydrogen 'bonding' is the attraction between negative and positive dipoles, so it is not really a 'bond'
NEXT SCRIBE, (Drumroll please), is Juliette
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