Dipole Moments

[Doreen Liu 4D]

Do CH3Cl, CH2Cl2, and CHCl3 all have dipole moments because of the lone pairs on the chlorine?

[LNgo 1G]

Dipole moments are created from differences in electronegativity, so since Cl is more electronegative than C and H, there will be a dipole moment in the direction of the Cl atoms.

[SMIYAZAKI_1B]

They will all have dipole moments; however, the degree of which electrons are pulled towards one certain direction is different because chlorine can attract electrons more than hydrogen.

[Sion Hwang 4D]

All of these molecules have a central C atom bonded to hydrogen atom(s) and Cl atom(s). There is a dipole moment due to the difference in electronegativity between Cl and C.
The difference in electronegativity between C and Cl is large enough that it is a polar covalent bond. This means that there will be an unequal sharing of electrons in the C-Cl bond, where Cl will tend to have greater pull on the electrons. Hence, the positive dipole moment will be formulated in the C, and the dipole will have a negative side in the Cl.
The difference in electronegativity between C and H is not great enough for a dipole to be formed.

[JinwooLee_1F]

CH3Cl and CHCl3 are obvious because if you look at the lewis structure since Cl is more electronegative, the molecule will have unequal "pull" of electrons. For CH2Cl2, you have to look at the VESPR model, which will show that they have unequal pull so it will have dipole moment.