- Orientational Polarization Definition: Orientational polarization is the alignment of permanent dipole moments in molecules along the direction of an applied electric field.
- Molecular Structure and Dipole Moments: Molecules like water have a bent structure resulting in permanent dipole moments due to the uneven distribution of charges.
- Effect of Electric Field: An external electric field causes molecules with permanent dipole moments to align with the field, creating orientational polarization.
- Examples of Molecules: Water and nitrogen dioxide are examples of molecules with permanent dipole moments due to their structural characteristics.
- Torque on Dipole Moments: The applied electric field exerts a torque on the permanent dipole moments, leading to their alignment with the field.
Before discussing orientational polarization, we need to look at the structure of some molecules. Take an oxygen molecule, for example. Each oxygen atom has 6 electrons in its outer shell. Two oxygen atoms form a double covalent bond, making an oxygen molecule. The distance between the nuclei of the two atoms is 121 picometers. However, there’s no permanent dipole moment because both ends of the molecule are equally charged. Hydrogen and nitrogen molecules also have no net dipole moment for the same reasons. Now, let’s consider the structure of a water molecule.
A water molecule has a bent structure. The oxygen atom forms covalent bonds with two hydrogen atoms. The oxygen side of the molecule is slightly negative, while the hydrogen sides are slightly positive. This creates two dipole moments pointing from the oxygen atom to the hydrogen atoms.
The angle between these two dipole moments is 105 degrees. The result is a permanent dipole moment in each water molecule, even without an external electric field. Molecules like nitrogen dioxide have similar permanent dipole moments for the same reason.
When an external electric field is applied, molecules with permanent dipole moments align themselves with the field. This happens because the electric field exerts a torque on the dipole moments. This alignment process is called orientational polarization.
