When do dipole moments occur

The Debye characterizes size of dipole moment. If the charge separation were increased then the dipole moment increases linearly :. From the electronegativities of oxygen and hydrogen, the difference is 1. Next, because the oxygen is the more electronegative atom, it exerts a greater pull on the shared electrons; it also has two lone pairs of electrons.

From this, it can be concluded that the dipole moment points from between the two hydrogen atoms toward the oxygen atom. Using the equation above, the dipole moment is calculated to be 1. A molecule that contains polar bonds, might not have any overall polarity, depending upon its shape. The simple definition of whether a complex molecule is polar or not depends upon whether its overall centers of positive and negative charges overlap.

If these centers lie at the same point in space, then the molecule has no overall polarity and is non polar.

If a molecule is completely symmetric, then the dipole moment vectors on each molecule will cancel each other out, making the molecule nonpolar. A molecule can only be polar if the structure of that molecule is not symmetric. The central carbon will have a net positive charge, and the two outer oxygen atoms a net negative charge. However, since the molecule is linear, these two bond dipoles cancel each other out i.

The atom with larger electronegativity will have more pull for the bonded electrons than will the atom with smaller electronegativity; the greater the difference in the two electronegativities, the larger the dipole.

This is the case with polar compounds like hydrogen fluoride HF , where the atoms unequally share electron density. Physical chemist Peter J. Debye was the first to extensively study molecular dipoles. Bond dipole moments are commonly measured in debyes, represented by the symbol D.

Molecules with only two atoms contain only one single or multiple bond, so the bond dipole moment is the molecular dipole moment. They range in value from 0 to 11 D. At one extreme, a symmetrical molecule such as chlorine, Cl 2 , has 0 dipole moment. Quick links. Email Link. When do dipole moments occur? The dipole moment of an entire molecule is made up of two bond moments -vector quantities having both magnitude and direction. Thus, a measured dipole moment is equal to the vector sum of the bond moments that comprise it.

Bond moments are vector quantities, possessing both magnitude and direction. Therefore, it's possible for a molecule to have bond moments and yet to be non-polar, if the individual bond moments in the molecule are equal in magnitude but opposite in their direction, therefore cancelling each other out.

Thus, the sum is 0 and there is no dipole moment.