Main Difference – Polar vs Nonpolar Bonds
Both polar bonds and non-polar bonds are two types of covalent bonding between atoms. In covalent bonding, the electrons are shared between the two atomic species involved, instead of a complete giveaway or acceptance of electrons. However, depending on the types of atoms involved, the shared pair of electrons will not be residing at the centre of the bond all the time. Some elements have a higher affinity towards electrons than the others. Therefore, the electrons within a bond tend to get attracted towards elements with a higher affinity towards electrons. And as a result, the bond shows an imbalance in terms of the position of electrons. This phenomenon is called ‘polarity’. The bonds that exhibit this nature are polar bonds and the bonds where the electrons reside in the centre without being bias towards either side of the bond are called non-polar bonds. Therefore, the main difference between polar and nonpolar bonds is that polar bonds occur between elements with different electronegativity whereas non-polar bonds occur between with the same electronegativity.
What are Polar Bonds
Polar bonds are a type of covalent bond that occurs between two elements when their electronegativity is different to each other. The term electronegativity refers to the affinity towards electrons. The atoms with high electro-negativity tend to attract electrons more than the ones with less electronegativity. Fluorine is known as the most electronegative element.
When a covalent bond is made between two atoms, electrons are being shared between them and these shared electrons usually reside within the space between the two atoms involved in the bond. This is more or less like an electron cloud. Therefore, when one element tends to attract electrons more than the other, the density of the electron cloud shifts towards the element with higher electron affinity. Thereby the electron distribution gets distorted.
As a result, there is a light charge built on either corner of the bond, a negative charge at the end where the electronegativity is high and a complementary positive charge on the other side respectively. These polarized bonds are able to form strong intermolecular interactions such as ’H bonds’. Polarized bonds are said to contain a ‘dipole moment’ in them, and each element involved in the bond is called the ‘dipoles’. However, it is not in all cases that polarized bonds lead to the formation of a polar compound. This depends on how the bonds are oriented within the atom. If it is in such a way that the dipole forces are cancelled out, then even though the compound has polar bonds, the compound itself will not be called a polar compound.
What are Non-Polar Bonds
These are a type of covalent bonds that occur between two elements when their electronegativity is the same. Therefore, usually non-polar bonds occur when the atoms involved in the bond are similar. These type of compounds are called ‘diatomic compounds’. In this case, the electrons being shared tend to reside in the centre of the bonding plane maintaining a balanced/centralized electron cloud. Hence, no distortion in the cloud can be seen.
There is also no build-up of charge at the poles, and the bond remains neutral. However, due to the instantaneous movements of the electron cloud, it is possible to have instantaneous changes at the poles, and these give rise to intermolecular attractions between non-polar compounds such as Van der Waals Interactions. In general, all compounds containing non-polar bonds are non-polar compounds.
Difference Between Polar and Nonpolar Bonds
Polar bonds are covalent bonds between elements that have different electronegativity.
Non-polar bonds are covalent bonds between elements that have the same electronegativity, in other words between similar atoms.
Nature of Electron Cloud
The electron cloud of a polar bond is distorted.
The electron cloud of a non-polar bond is not distorted.
Polar bonds have charges building up at their poles.
Non-polar bonds do not have such a charge build up.
Polar bonds have a dipole moment.
Non-polar bonds do not have a dipole moment.
H bonds occur between charged poles of polar bonds.
Van der Waal interactions are commonly seen between non-polar compounds.
“Water-elpot-transparent-3D-balls”. (Public Domain) via Commons
“Ethane-A-3D-balls” by Ben Mills – Own work. (Public Domain) via Wikimedia Commons