Dipole-Dipole

[Claudeth Martinez 1D]

Hello,

How do I know when a lewis structure has a dipole-dipole moment?

[klarratt2]

Dipole moments arise from differences in electronegativity. The larger the difference in electronegativity, the larger the dipole moment. The distance between the charge separation is also a deciding factor into the size of the dipole moment. The dipole moment is a measure of the polarity of the molecule.

When atoms in a molecule share electrons unequally, they create what is called a dipole moment. This occurs when one atom is more electronegative than another, resulting in that atom pulling more tightly on the shared pair of electrons, or when one atom has a lone pair of electrons and the difference of electronegativity vector points in the same way.

Typically, if a Lewis structure is asymmetric, it will be polar and have a dipole moment (like in H2O). Symmetric molecules have dipoles that cancel with each other, making the nonpolar (like in C2H6).

[Leslie Cheng 4B]

Well, a dipole-dipole interaction is a type of intermolecular interaction, which means it's going to be between two molecules. You could look at a lewis structure and see if it's polar (usually polar molecules are asymmetrical and have dipole moments that don't cancel) because polar molecules have permanent dipole moments and can therefore form dipole-dipole interactions. Dipole-dipole interactions occur between two molecules that have permanent dipole moments.

[mbaker4E]

Usually, if a molecule is asymmetrical or has lone pairs of electrons then it will be polar. If two polar molecules come together, they can form a dipole-dipole interaction from the partially positive side of the molecule attracting a partially negative side of another polar molecule.