Polarity and Molecular Shape

[melodyzaki2E]

How does polarity affect the molecular shape of molecules? Does it change their VSEPR model at all?

[janeane Kim4G]

yes! Polarity does affect the shape of the vsepr. This can best be observed between the difference in structure between CO2 and H2O. CO2 has C as the central atom and double bonds with the 2 Oxygen next to it. In this case, the C has no lone pairs and the poles are evenly distributed between the molecule.
( δ-) O=C(δ +) =O (δ -)
as you can see, the dipole moment will push towards the 2 oxygens, giving CO2 a linear structure. However, for H2O the oxygen in this case has 2 lone pairs, which causes the O atom to “pull” the electrons towards it, giving it a permanent negative charge in the O and slight positive charges in the H2 area. In this case, the shape cannot be linear because oxygen’s lone pair electron cloud pushes the H atoms closer together, to form a “bent” shape instead.
(↑ e-) O (δ-)
(δ+) H H (δ+)