Intermolecular Forces and Properties of Matter
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Transcript of Intermolecular Forces and Properties of Matter
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Intermolecular Forces and Properties of Matter
Sec. 4.4, 4.5 and 4.6 of text
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Electronegativity, Bond Polarity and Polar Molecules
re-cap: (silly Gr. 10/11 rules)electroneg. diff. > 1.7 (?): ionicbetween 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 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.