Polar/Nonpolar Bond vs Molecule [ENDORSED]

[Leah Thomas 2E]

Can someone explain the different between a polar/nonpolar bond vs a polar/nonpolar molecule because I know that a molecule may be polar but the bond is nonpolar but how?

[Vivian Nguyen]

A non polar bond occurs when the electrons are equally shared while a polar bond occurs when the electrons are unequally shared due to differences in electronegativity. For example, H2 would be nonpolar because the atoms have the electronegativity. Meanwhile, OH is polar because oxygen is much more negative, so the electrons will be more displaced towards oxygen.

In terms of nonpolar/polar molecules it depnds on the dipole moments of the bonds in the molecule. I'm not sure about molecules being polar and having nonpolar bonds, but I know there are cases where molecules can be nonpolar while having polar bonds. Dr.Lavelle went through an example using trans-Dichloroethene versus cis-Dichloroethene.

http://people.uwplatt.edu/~sundin/images/vsprcl2e.gif Here's an image that might help.

In trans-dichloroethene, the vectors that represent dipole moments cancel each other out, making it a nonpolar molecule despite having polar bonds.

Hope this'll help!

[Chem_Mod]

"Dr. Lavelle went through an example using trans-Dichloroethene versus cis-Dichloroethene."

Yep, and I believe it is a good example.
:-)

[Sonja Kobayashi 1H]

The polarity of a bond refers to one specific bond and the differences between their electronegativity. The polarity of a molecule refers the the molecule as a whole. Therefore, a non-polar molecule can contain polar bonds if the dipoles cancel out!