CH301H - Principles of Chemistry I: Honors
Fall 2013, Unique 52195

Lecture Summary, 10 September 2013

Covalent Bonding and Polarity:  Most bonds are neither completely ionic nor completely covalent, but something in between.  When two atoms with different electronegativities form a bond, the atom with the higher electronegativity will tend to sequester the electrons in the bond.  This creates a partial negative charge on the higher electronegativity atom and a partial positive charge on the lower electronegativity atom.  This distribution of partial charge in turn creates a dipole moment, a vector that points from the negative end of the atom to the positive end.  Molecular dipole moments can be measured experimentally.  For molecules larger than a diatomic, individual bond dipole moments can be inferred from knowing molecular geometry (something we will discuss in more detail next week).