What is Polar?
A molecule or its chemical groups have an electric dipole moment with a negatively charged end and a positively charged end when polar, which in chemistry is the separation of electric charge.
Because the bonded atoms’ electronegativity differs, polar compounds must have one or more polar bonds. If the bond dipoles cancel one other out via symmetry, molecules with polar bonds are not polar.
Dipole-dipole intermolecular forces and hydrogen bonding are how polar molecules communicate. Many physical characteristics, including surface tension, solubility, and melting and boiling points, are based on polarity.
When two atoms do not share any electrons equally in a covalent bond is a polar molecule. A dipole bond is formed in which one part of a molecule carries a slight positive charge, and the other part carries a negative charge.
This happens due to the difference in the electronegativity of atoms. When there is an extreme difference, it forms an ionic bond, while a lesser difference forms a polar covalent bond.
If the difference in electronegativity is .5 and 2.0, atoms form a polar covalent bond. But if the electronegativity difference is more significant than 2.0, the bond that forms is ionic.
The ionic compounds are highly polar molecules. Examples of polar bonds are water H2O, ammonia NH3, sulphur dioxide SO2, etc.
What is Nonpolar?
When there is an equal sharing of electrons between two atoms of diatomic molecules because of the asymmetrical arrangement of polar bonds to form a complex molecule.
The bond is considered nonpolar if two or more atoms in a bond share the same electronegativity of less than 0.4. The bond in chlorine is nonpolar. Two chlorine atoms make up chlorine.
Since there is no difference in the electronegativity of the two atoms, the electrons are distributed equally. Nonpolar molecules will form when atoms have the same electronegativity.
When the electronegativity between two atoms is less than 0.5, then the bond is nonpolar. Atoms sharing polar bonds can also organise themselves to create nonpolar molecules by having their electric charges balance one another.
Nonpolar bonding has high vapour pressure, low surface tension, low boiling, and low melting points. Nonpolar molecules have no abundance of charges at their opposite ends and do not interact with other nonpolar molecules.
Nonpolar molecules include carbon dioxide CO2, Benzene C6H6, carbon tetrachloride CCL4, etc.
Difference Between Polar and Nonpolar
The electron density in polar molecules has a uniform distribution, while the nonpolar molecules have an unequal electron distribution and density.
The polar compounds are arranged asymmetrically, while the nonpolar compounds are symmetrical.
When there is no dipole moment, the molecule is polar, e.g., water. Compared to polar molecules, the nonpolar molecule has significant dipole moments, e.g., carbon tetrachloride CCL4.
In nonpolar molecules, identical atoms are present around the central atom, which bond the atom without any unshared pairs of electrons; e.g Carbon tetrachloride is its example.
In contrast, the polar molecules are asymmetrical, and they contain a lone pair of electrons on central atoms and possess different electronegativities e.g.hydrogen fluoride HF.
Comparison Between Polar and Nonpolar
| Polar | Nonpolar |
| Polar molecules are asymmetrical. | Nonpolar molecules are symmetrical. |
| It has electrical poles. | It does not have electrical poles. |
| It has positive and negative charges. | It does not have charges. |
| Dipole moment is present. | No dipole moment. |
| There is charge separation. | No charge separation. |
| An example is water. | An example is oil. |
References
^ Ingold, C. K.; Ingold, E. H. (1926). “The Nature of the Alternating Effect in Carbon Chains. Part V. A Discussion of Aromatic Substitution with Special Reference to Respective Roles of Polar and Nonpolar Dissociation; and a Further Study of the Relative Directive Efficiencies of Oxygen and Nitrogen”. J. Chem. Soc. 129: 1310–1328. doi:10.1039/jr9262901310.