# Dipole moment important points and rules to followAnd what about the dipole moment of noble gases when combined

Shivangi Khatter
4 years ago
dear student
Thebond dipole moment[1]uses the idea ofelectric dipole momentto measure thepolarityof a chemical bond within amolecule. It occurs whenever there is a separation of positive and negative charges. The bond dipoleμis given by:

{\displaystyle \mu =\delta \,d} [\mu =\delta \,d] .

The bond dipole is modeled as +δ — δ- with a distancedbetween thepartial charges+δ and δ-. It is a vector, parallel to the bond axis, pointing from minus to plus,[2]as is conventional for electric dipole moment vectors.

Chemists often draw the vector pointing from plus to minus.[3]This vector can be physically interpreted as the movement undergone by electrons when the two atoms are placed a distancedapart and allowed to interact, the electrons will move from their free state positions to be localised more around the moreelectronegativeatom.

The SI unit for electric dipole moment is the coulomb-meter. This is too large to be practical on the molecular scale. Bond dipole moments are commonly measured indebyes, represented by the symbol D, which is obtained by measuring the charge{\displaystyle \delta } [\delta] in units of 10−10statcoulomband the distancedinAngstroms. Note that 10−10statcoulomb is 0.208 units of elementary charge, so 1.0 debye results from an electron and a proton separated by 0.208 Angstrom. A useful conversion factor is 1 D = 3.335 64×10−30Cm.[4]

For diatomic molecules there is only one (single or multiple) bond so the bond dipole moment is the molecular dipole moment, with typical values in the range of 0 to 11D. At one extreme, a symmetrical molecule such aschlorine,Cl
2, has zero dipole moment, while near the other extreme, gas phasepotassium bromide, KBr, which is highly ionic, has a dipole moment of 10.5D.[5]

For polyatomic molecules there is more than one bond, and the totalmolecular dipole momentmay be approximated as the vector sum of individual bond dipole moments. Often bond dipoles are obtained by the reverse process: a known total dipole of a molecule can be decomposed into bond dipoles. This is done to transfer bond dipole moments to molecules that have the same bonds, but for which the total dipole moment is not yet known. The vector sum of the transferred bond dipoles gives an estimate for the total (unknown) dipole of the molecule