A dipole moment is a result of unequal electron distribution, which occurs due to differences in electronegativity between chemically-bonded atoms
. It is a vector quantity, as it has both magnitude and direction
. Dipole moments can occur in ionic bonds or covalent bonds and are caused by differences in electronegativity between atoms
. There are two types of dipole moments:
- Bond Dipole Moment : A measure of the polarity of a chemical bond between two atoms in a molecule. It is the product of the magnitude of the charge and the distance between the centers of the positive and negative charges
- Molecular Dipole Moment (Net Dipole Moment) : A measure of the polarity of the entire molecule. In polyatomic molecules, it is the vector sum of all bond dipole moments present in the molecule
To calculate the dipole moment of a chemical bond, the following formula is used
: μ⃗=Qr\vec{\mu}=Qrμ=Qr where:
- μ⃗\vec{\mu}μ is the dipole moment vector
- QQQ is the magnitude of the separated charge
- rrr is the distance of separation between the charges
The SI unit for dipole moment is the coulomb-meter (C·m), but it is most commonly measured in debyes (1 debye is equal to 3.34×10−293.34\times 10^{-29}3.34×10−29 coulombs)
. Dipole moments are important in understanding the polarity of molecules and the distribution of charge within them
