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Intermolecular Forces for 11U
Sec. 2.4 of text
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Electronegativity, Bond Polarity and Polar Molecules
re-cap: (Gr. 10/11 rules) electroneg. diff. > 1.7: ionic between 0.4 and 1.7: polar (covalent) <0.4: non-polar (purely or almost purely covalent) but… in CO2 the molecular geometry allows dipoles to cancel, therefore it is nonpolar
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Nonpolar vs. Polar Molecules
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Intramolecular vs Intermolecular
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Intermolecular Forces or van der Waals forces or non-covalent forces
Ionic Compounds are not “molecules” -- It is debatable whether ionic interactions are to be seen as intermolecular forces, most consider them rather as a special kind of chemical bonding. Molecules Dipole-dipole interactions Hydrogen Bonds (with N, O or F) London (forces) who himself called it dispersion
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From a real textbook (Brown, LeMay & Bursten; 1994)
Boiling points of the group 4A (bottom) and 6A (top) hydrides as a function of molecular wt. Wasup with this? If not for H-bonds, b.p of water = -100°C
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Hydrogen Bonds & DNA
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Intermolec. Ppty’s & Boiling Points
More electrons and greater M.W. allows for more London forces.
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