CHEM 0120 1nd Edition Lecture 3 Outline of Last Lecture I Chemical Bonds II Acids and Bases III Polyatomic Ions Outline of Current Lecture I Dispersion Forces II Dipole Dipole Interactions III Hydrogen Bonding Current Lecture I Dispersion Forces A Momentary attractive forces between molecules B Everything has dispersion forces C Example pentane momentary electron position causes attractive forces II Dipole Dipole Interactions A Structure 1 Polar bonds a Polar covalent bond with bent structure net dipole movement b Polar covalent bond with linear structure no net dipole movement 2 Geometry 3 Same direction and magnitude add dipole These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 4 Different direction and same magnitude cancel dipole B Example Water Contains polar bonds that result in a net dipole movement C Example Carbon Dioxide Contains polar bonds but dipoles cancel III Hydrogen Bonding A Results from interaction between a hydrogen atom bound to a small electronegative atom such as N O F and a lone pair of electrons on another small electronegative atom B Strongest intermolecular force C Example Hydrogen Bond