POLARITY We’ve already talked about electronegativity and how to predict whether a bond is polar or nonpolar. For example: Pure covalent bond = sharing of electrons between two identical atoms (with the same electronegativity and no difference in charge) i.e. O2 Polar covalent bond = sharing of electrons between two or more different atoms with a difference in electronegativity. i.e. HCI Just as a bond can be polar or nonpolar, we can also classify an entire molecule as polar or nonpolar. A molecule is said to be polar if the overall (net) effect of all the dipole moments in each bond do not cancel each other out. To determine polarity of a molecule, we first determine the molecular geometry and then draw an arrow pointing from the positive to negative side of each bond. The overall effect of each dipole is then considered. After you draw the molecular geometry, consider what would happen to the central atom if you tied a rope to each of the outside atoms and pulled. Or, if you’re morbid (like the textbook I stole these pictures from) consider what would happen to the man below: He stays He put… moves… meaning the SO3 molecule is nonpolar. meaning the SOCI, molecule is polar.

Do all of the man’s limbs in the picture above rip off at the same time? If they do, then the molecule has no dipole moment is non-polar). If one or more of his limbs rips off first, then the molecule has a nonzero dipole moment (is polar). Examples: Classify each molecule below as polar or non-polar. Justify your answers using 3-D VSEPR models and dipole moment vectors. CC14 CHCI SnClz: H2O NO3 BF3 SiO2 PF5 IFs SF4