Difference Between Polar and Nonpolar Dielectrics

Main Difference – Polar vs Nonpolar Dielectrics

Dielectrics are electrical insulators. They are not electricity conducting materials since they have no free electrons to conduct electricity. A dielectric can be polarized by applying an electric field. There are two types of dielectrics as polar dielectrics and nonpolar dielectrics. Polar dielectrics are polar compounds that cannot conduct electricity. Nonpolar dielectrics are nonpolar compounds that cannot conduct electricity. The main difference between polar and nonpolar dielectrics is that polar dielectrics have an asymmetric shape whereas nonpolar dielectrics have a symmetric shape.

Key Areas Covered

1. What are Polar Dielectrics
     – Definition, Polarity, Examples
2. What are Nonpolar Dielectrics
     – Definition, Polarity, Examples
3. What is the Difference Between Polar and Nonpolar Dielectrics
     – Comparison of Key Differences

Key Terms: Asymmetric, Dielectrics, Insulators, Nonpolar, Polar, Polarity, Symmetric

What are Polar Dielectrics

Polar dielectrics are polar compounds that cannot conduct electricity. No current can flow through them because there are no free electrons to conduct electricity. The major reason for a material to be a polar dielectric is its shape. The shape of these dielectrics is asymmetric.

When a polar dielectric molecule is considered, the polarity of the molecule is determined by the shape or the geometry of the molecule. A polar covalent chemical bond is formed when two different atoms are bonded to each other. Different elements have different electronegativity values. Electronegativity is the affinity for electrons. The atom with higher electronegativity will attract the bond electrons towards itself. Then the atom with the lower electronegativity gets a partial positive charge (due to electron deficiency), and the more electronegative atom gets a partial negative (due to high electron density). This is what we call polarity of the covalent bond. If a molecule is composed of several polar covalent bonds, the arrangement of these bonds (shape of the molecule) determines whether it is a polar molecule or not. If this molecule cannot conduct electricity, then it is a polar dielectric.

Figure 1: NH₃ is a Polar Dielectric Molecule

Ammonia molecule is a good example of a polar dielectric. It has no free electrons that can conduct electricity. It is a polar molecule because nitrogen atom is more electronegative than hydrogen atom and the arrangement of the three N-H bonds is trigonal pyramidal.

What are Nonpolar Dielectrics

Nonpolar dielectrics are nonpolar compounds that cannot conduct electricity. No current can flow through them because there are no free electrons to conduct electricity. The major reason for a material to be a polar dielectric is its shape. The shape of these dielectrics is symmetric.

Nonpolar dielectric molecules are nonpolar because they have a symmetric geometry. For example, CO₂ is a linear molecule having two C-O bonds. C-O bond is a polar bond due to the difference between electronegativity values of the carbon and oxygen. But, since the arrangement of the bonds is linear, the net polarity is zero. Therefore, it is a nonpolar molecule. It does not conduct electricity. Hence, it is a nonpolar dielectric molecule.

Figure 2: Benzene is a Nonpolar Dielectric

Some examples of nonpolar dielectric compounds include methane, benzene, carbon dioxide, and many other nonpolar compounds that have no free electrons capable of conducting electricity.

Difference Between Polar and Nonpolar Dielectrics

Definition

Polar Dielectrics: Polar dielectrics are polar compounds that cannot conduct electricity.

Nonpolar Dielectrics: Nonpolar dielectrics are nonpolar compounds that cannot conduct electricity.

Shape

Polar Dielectrics: The shape of polar dielectrics is asymmetric.

Nonpolar Dielectrics: The shape of nonpolar dielectrics is symmetric.

Polarity

Polar Dielectrics: Polar dielectrics are polar.

Nonpolar Dielectrics: Nonpolar dielectrics are nonpolar.

Examples

Polar Dielectrics: Ammonia and HCl are good examples of polar dielectrics.

Nonpolar Dielectrics: Benzene, methane, carbon dioxide are good examples of nonpolar dielectrics.

Conclusion

Dielectrics are compounds that cannot conduct electricity. These dielectrics are found as polar dielectrics or nonpolar dielectrics depending on the polarity of the molecules. The main difference between polar dielectrics and nonpolar dielectrics is that polar dielectrics have an asymmetric shape whereas nonpolar dielectrics have a symmetric shape.

References:

1. “Dielectric.” Chemistry Learning, Available here.
2. “Dipole Moment | Dielectric Material | Polar and Non Polar Molecules.” Physics, Byjus Classes, 7 Aug. 2017, Available here.
3. “What are Polar and Non Polar Dielectrics?” The Bigger, Available here.

Image Courtesy:

1. “NH3 polarity” By すじにくシチュー – Own work (CC0) via Commons Wikimedia
2. “Benzene-2D-flat” By Benjah-bmm27 assumed (based on copyright claims)  (Public Domain) via Commons Wikimedia