The key difference between polarizability and dipole moment is that polarizability is the measure of how effortlessly an electron cloud is distorted by an electric field, whereas dipole moment is the separation of positive and negative charges in a system.
Polarizability and dipole moment are two important terms in chemistry that are described in relation to atoms, molecules, and their electron clouds.
CONTENTS
1. Overview and Key Difference
2. What is Polarizability
3. What is Dipole Moment
4. Polarizability vs Dipole Moment in Tabular Form
5. Summary – Polarizability vs Dipole Moment
What is Polarizability?
Polarizability can be described as the tendency of matter to acquire an electric dipole moment in proportion to the applied field when an electric field is applied. This phenomenon is a property of all matter when we consider that matter is built up of elementary particles having an electric charge by means of protons and electrons.
In the presence of an electric field, negatively charged electrons and positively charged atomic nuclei undergo the effect of opposite forces and charge separation. Polarizability is responsible for the dielectric constant of the material and the refractive index when high frequencies are considered.
Moreover, the polarizability of an atom or a molecule is the ratio of the induced dipole moment and the local electric field. When a crystalline solid is considered, we can identify the dipole moment per unit cell. Furthermore, the local electric field can be observed by a molecule that generally differs from the macroscopic electric field we can measure externally.
Similarly, magnetic polarizability refers to the tendency of the magnetic dipole moment to appear in proportion to an external magnetic field. Electric polarizability and magnetic polarizability determine the dynamic response of a bound system to external fields and provide insight into the internal structure of the molecule.
What is Dipole Moment?
A dipole moment can be described as the separation of electrical charges. The charge separation may take place between two ions in an ionic bond or two atoms in a covalent chemical bond. A dipole moment arises due to differences between electronegativity values of different atoms that form chemical bonds. The greater the difference between electronegativity values, the greater the dipole moment. The dipole moment measures the polarity of a molecule. The dipole moment of a molecule is calculated using the following equation.
μ = Σq.r
μ is the dipole moment, q is the magnitude of charge, and r is the position of the charge. Here, μ and r are vectors, which are quantities having a direction as well as a magnitude.
Figure 01: Electric Field of an Electric Dipole
But sometimes, the term dipole moment is used to name the measure of the magnetic polarity of a system of charges. The magnetic dipole moment determines the torque that a magnet experiences in an external magnetic field. (Torque=moment; a rotational force).
What is the Difference Between Polarizability and Dipole Moment?
Polarizability and dipole moment are two important terms. The key difference between polarizability and dipole moment is that polarizability is the measure of how effortlessly an electron cloud is distorted by an electric field, whereas dipole moment is the separation of positive and negative charges in a system.
The following table summarizes the difference between polarizability and dipole moment.
Summary – Polarizability vs Dipole Moment
Polarizability is the tendency of matter to acquire an electric dipole moment in proportion to the applied field when an electric field is applied, while dipole moment is the separation of electrical charges. The key difference between polarizability and dipole moment is that polarizability is the measure of how effortlessly an electron cloud is distorted by an electric field, whereas dipole moment is the separation of positive and negative charges in a system.
Reference:
1. “Polarizability.” Chemistry LibreTexts, Libretexts, 4 May 2022.
Image Courtesy:
1. “VFPt dipole animation electric” By Geek3 – Own work (CC BY-SA 3.0) via Commons Wikimedia