The main difference between polar and nonpolar bonds is their electronegativity. The greater the electronegativity difference between the bonded atoms greater is the polarity.
Both polar and nonpolar bonds are covalent bonds. However, polar bonds have unsymmetrically distributed electron pairs between two nuclei where electron pair(s) are attracted to the more electronegative atom. Whereas, in nonpolar bonds, electron pairs are equally distributed between the two bonded nuclei.
Polar vs nonpolar bonds
| Polar bond | Non-polar bond |
| Polar bonds are less stable | Non-polar bonds are more stable |
| Unequal sharing of electron pairs | Equal sharing of electron pairs |
| Have positive and negative poles | Neither positive nor negative poles |
| Contain strong hydrogen bonding interaction | Contain weak van der waal interaction |
| It has charge separation | No charge separation |
| It has a dipole moment | No dipole moment |
| It contains highly electronegative and electropositive atoms | It contains either similar or atoms with less E.N difference |
| The sizes of bonding atoms are essentially different | The sizes of bonding atoms are mostly equal |
| Polar molecules have high melting and boiling points | Non-polar molecules have low melting and boiling points |
| They have a high surface tension | They have a low surface tension |
| Always have a low vapor pressure | Always have a high vapor pressure |
| E.N difference is greater than 0.4 | E.N difference is less than 0.4 |
| Exist in the forms of ionic bonds and polar covalent bonds | Exist in the forms of non-polar covalent bonds |
| Water, ammonia, hydrogen fluoride, and sulfur dioxide are the best examples of polar bonds | Hydrogen, nitrogen, oxygen, and all noble gas molecules are the best examples of non-polar bonds |
Polar bond
Among many types of bonds, polar bonds are the bonds with atoms having a significant difference in their electronegativity values. This difference results in charge separation, eventually forming partial positive and negative poles. The strength of the bond depends upon the ΔE.N of the atoms. The greater electronegativity difference corresponds to a stronger bond.
Polar bonds can be either polar covalent or ionic in nature. Bonds having ΔE.N > 0.4 are the polar covalent bonds and those with ΔE.N > 1.8 are ionic bonds.
Examples of Polar Covalent Bond
- Water (H2O)
- Ethanol (C2H6O)
- Ammonia (NH3)
- Sulfur dioxide (SO2)
- Hydrogen sulfide (H2S), etc.
Examples of Ionic Bond
- Lithium fluoride (LiF)
- Sodium chloride (NaCl)
- Potassium bromide (KBr)
- Beryllium fluoride (BeF2)
- Magnesium chloride (MgCl2), etc.
Nonpolar bond
In nonpolar bonds, the electrons are equally distributed between the nuclei of the atoms and they almost have the same electronegativity values (i.e. ΔE.N < 0.4). There is no charge separation and thus, no positive and negative poles exist across the molecules.
Nonpolar bonds are covalent in nature but with lesser or no polarity at all.
Examples of Nonpolar bond
- All noble gases are examples of nonpolar bonds.
- Homonuclear diatomic molecules like H2, N2, O2, etc.
- Benzene and toluene have a non-polar bond character
- Carbon tetrachloride (CCl4)
- Methane (CH4)
- Ethylene (C2H4), etc.
Molecules with the highest electronegativity difference
| Bond | Electronegativity Difference | Polarity |
| C–C | 0.0 | Non-polar |
| C–H | 0.4 | Polar |
| C–N | 0.5 | Polar |
| Si–C | 0.7 | Polar |
| C–O | 1.0 | Polar |
| Si–O | 1.7 | Highly polar |
Geometrical non-polarity in molecules
Molecules may have polar bonds but still be overall nonpolar in nature. This is because of the geometrical non-polarity. The reason of this phenomenon is that the geometrically arranged bonds cancel each other’s effect. The dipole moment of molecules is calculated by the vector addition of all polar bonds and hence, the result may not be as expected.
For example, in a CO2 molecule, the bonds are polar in nature. But the molecule is nonpolar as a whole. The two C=O are at an angle of 180º; they cancel each other’s effect and thus, the dipole moment of CO2 is 0 debye.
Key Differences between polar and nonpolar bonds
Concepts Berg
What are polar and nonpolar covalent bonds?
Polar covalent bond has an electronegativity difference ranging between 0.4 to 1.7 and they have positive and negative poles across the molecule. On the other hand, a nonpolar bond has an electronegativity difference of less than 0.4 and there is no polarity.
Is water a polar molecule?
Yes, water is a polar molecule as it has unequal sharing of electron pairs. The V shape of water showing a dipole moment is another reason that the water is a polar molecule.
How can you tell if a bond is polar or nonpolar?
A bond can be polar if the E.N difference of the bonded atoms is greater than 0.4. We can also observe the molecule if it has partial positive and partial negative charges.
How can a molecule have polar bonds but overall be nonpolar and vice versa?
It can be explained through the symmetry of the compound. If the compound is polar due to the difference in electronegativity of the atoms but it has a symmetrical shape, it causes geometrical non-polarity to exist there. As the result, it will cancel the effect of polarity. For example, CCl4, CO2, etc.
Which type of bond is stronger, polar or nonpolar?
The polar bond is stronger than a nonpolar bond as there is an extra force of attraction present in the polar bonds like positive and negative charges.
Is the carbon-phosphorus bond polar or nonpolar bond?
The electronegativity difference of carbon-phosphorus is about 0.3. A bond can be polar if the E.N difference is greater than 0.4. By comparing their E.N difference, we can say carbon-phosphorus is nonpolar bond.
Is SeCl2 a polar or nonpolar molecule?
SeCl2 is a polar molecule because it has an E.N difference greater than 0.4 among atoms. The partial positive and partial negative poles are present across the molecule as a result.
Are ionic bonds polar or nonpolar?
All ionic bonds are polar. The asymmetrical distribution of electron pairs in ionic compounds is due to the high electronegativity difference.
Is SO2 a polar or nonpolar molecule?
Sulfur dioxide is a polar molecule because of the electronegativity difference between sulfur and oxygen molecule exceeding 0.4 and the bent shape geometry.
What is the difference between the polarity of a bond and a dipole moment?
Polarity means how much a bond can have the ability to form poles whereas dipole moment is the measurement of the charge separation.
What are some examples of nonpolar bonds?
Non-polar bonds exist in:
-
- H2, N2, O2
- Benzene and toluene
- Carbon tetrachloride (CCl4)
- Methane (CH4)
- Ethylene (C2H4), etc.
What is the bond polarity of HCN? Is it a polar covalent, ionic, or nonpolar covalent bond?
HCN, hydrogen cyanide is a polar molecule because there is a huge difference between hydrogen and nitrogen atoms.
What is the polarity of bonds?
The polarity of bonds is the distribution of charge across its ends. It is the polarity of bonds that leads to intermolecular attractions.
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