intermolecular forces and properties of matter
DESCRIPTION
Intermolecular Forces and Properties of Matter. Sec. 4.4, 4.5 and 4.6 of text. Electronegativity, Bond Polarity and Polar Molecules. re-cap: (silly Gr. 10/11 rules) electroneg. diff. > 1.7 (?): ionic between 0.4 (?) and 1.7: polar (covalent) - PowerPoint PPT PresentationTRANSCRIPT
Intermolecular Forces and Properties of Matter
Sec. 4.4, 4.5 and 4.6 of text
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
Nonpolar vs. Polar Molecules
Intramolecular vs Intermolecular
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
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
Hydrogen Bonds & DNA
Intermolec. Ppty’s & Boiling Points
More electrons and greater M.W. allows for more London forces.