MOLECULAR SHAPE AND POLARITY MOLECULAR SHAPE AND POLARITY

MOLECULAR SHAPE AND POLARITY

MOLECULAR SHAPE AND POLARITY A molecule may have polar bonds, but it may not be polar Example: CO 2 is a nonpolar molecule, but each C=O bond is polar

MOLECULAR SHAPE AND POLARITY Example: CO 2 Use electronegativity to predict the polarity of each bond. Show the bond polarity as an arrow, pointing from the positive (δ +) to the negative (δ -) end of the bond. This arrow represents the _________

MOLECULAR SHAPE AND POLARITY Example: CO 2 - The above arrows are vectors - Adding these vectors together cancels them out -. : CO 2 is non-polar

MOLECULAR SHAPE AND POLARITY Example: H 2 O H - O-H bonds in water are polar bonds - 3 D shape = angular/bent shape - bond dipoles (vectors) add together to produce a molecular dipole (red arrow)

MOLECULAR SHAPE AND POLARITY Summary • the shape of the molecule and the polarity of the bonds are necessary to determine if a molecule is polar or nonpolar • in all _______molecules, the sum of the bond dipoles is zero and the molecule is nonpolar

MOLECULAR SHAPE AND POLARITY Summary bent trigonal pyramidal NO The molecule is polar. Is the shape symmetrical in 3 D? NO linear tetrahedral YES Are all the ∆EN bond values the same? YES The molecule is non-polar. See page 106 for a similar table

MOLECULAR SHAPE AND POLARITY Example: NH 3 1) Draw the Lewis structure 2) Based on the Lewis structure, draw the 3 D diagram

MOLECULAR SHAPE AND POLARITY Example: NH 3 3) Add the electronegativity of the atoms and assign δ+ and δ- to the bonds 4) Draw in the bond dipoles . : NH 3 is polar because it has polar bonds that do no cancel to zero.