B.P. H2O 100ºC H2S -62ºC H2Se -42ºC H2Te -2ºC Hydrogen Bonding …enhanced dipole-dipole interactions between molecules in which hydrogen is bonded to either nitrogen, oxygen or fluorine H2O 100ºC Both molecules exhibit dipole-dipole interactions and London dispersion forces…but H2Se, with a higher molar mass [hence more electrons], has greater LDF’s mm= 18.0 g H2S -62ºC Dipole-Dipole Interactions mm= 34.1 g Less polar molecule…lower b.p. predicted H2Se -42ºC Attractions between permanently polar molecules. mm= 81.0 g H2Te -2ºC mm= 129.6 g

B.P. He -270ºC N2 -196ºC Temporary Dipoles… Both nonpolar particles London Dispersion Forces He -270ºC Temporary Dipoles… Both nonpolar particles Creates attraction between particles, although generally weak ones N2 -196ºC More noteworthy when more electrons are around…

B.P. CH3F -78ºC CH3OH 65ºC Both polar molecules… mm= 34 g Both polar molecules… …with similar molar masses CH3OH 65ºC Hydrogen bonding here mm= 32 g