# Dipole Moments

Can someone explain how to determine if a compound has a dipole moment and how to determine how big or small it is (possibly numerical value)? I have a final tomorrow and I've looked this up on multiple website and cannot find any good explanation.

Bystander
Homework Helper
Gold Member
Tell us what you know so far, and somebody(ies) will try to make what you know work for you.

Tell us what you know so far, and somebody(ies) will try to make what you know work for you.
Honestly nothing.. I know it has something to do with polarity and molecular structure.

Bystander
Homework Helper
Gold Member
polarity and molecular structure.
Gets to right ballpark. "Polarity" is the separation of electric charges of opposite sign along an interatomic bond axis usually (occasionally over longer distances within a molecule), and obviously the molecular structure comes in when you're considering where these charge separations occur, and whether there is any sort of symmetry to the arrangement within a molecule that would add up to zero, no matter what magnitude individual dipoles might exhibit.

Every heteronuclear bond between two atoms (this could be within the structure of some larger polyatomic molecule) exhibits some sort of charge separation (electrons preferring to hang around one nucleus more than the other) that can be treated as if there were actually X.xxx negative charge (doesn't have to be a multiple of charge on electron) on one nucleus separated from X.xxx positive charge on another nucleus at a distance equivalent to the bond length; the product of the total charge difference and that bond length is dipole moment (units of charge x distance).

Does this make sense so far?

Gets to right ballpark. "Polarity" is the separation of electric charges of opposite sign along an interatomic bond axis usually (occasionally over longer distances within a molecule), and obviously the molecular structure comes in when you're considering where these charge separations occur, and whether there is any sort of symmetry to the arrangement within a molecule that would add up to zero, no matter what magnitude individual dipoles might exhibit.

Every heteronuclear bond between two atoms (this could be within the structure of some larger polyatomic molecule) exhibits some sort of charge separation (electrons preferring to hang around one nucleus more than the other) that can be treated as if there were actually X.xxx negative charge (doesn't have to be a multiple of charge on electron) on one nucleus separated from X.xxx positive charge on another nucleus at a distance equivalent to the bond length; the product of the total charge difference and that bond length is dipole moment (units of charge x distance).

Does this make sense so far?
Partially, but go on.

Bystander