Important Notes on Covalent Bonds, Types, Properties

All the elements that have very high ionization energies are incapable of transferring electrons and elements which have very low electron affinity cannot take up electrons. Atoms of such elements share their electrons with the atoms of other elements or with other atoms of the same element in such a way that both the atoms obtain octet configuration in their valence shell and achieve stability. The pair of electrons that participates in a covalent bond are called bonding pairs or shared pairs. This association by the sharing of electron pairs with different or same kinds is known as Covalent Bond.

Types of Covalent Bonds

Covalent bonds can be classified into 3 categories:

1.  Single Covalent Bond
2.  Double Covalent Bond
3.  Triple Covalent Bond

Click to Check – Periodic Table: Groups, Properties And Laws

Single covalent bonds are formed when only one pair of the electron is shared between the two participating atoms. This form of covalent bond has a smaller density and is weaker than a double and triple bond but it is the most stable bond.

Example: HCL molecule has one Hydrogen atom with one valence electron and one Chlorine atom with seven valence electrons. A single bond is formed between hydrogen and chlorine by sharing one electron in their valence shell.

Double Covalent Bond is formed when two pairs of electrons are shared between the two participating atoms. Double covalent bonds stronger than a single bond, but they are less stable.

Example: In the formation of the oxygen molecule, each oxygen atom has six electrons in their valence shell. Each atom requires two more electrons to complete their octet. Therefore the atoms share two electrons each to form the oxygen molecule. Since two electron pairs are shared there is a double bond between the two oxygen atoms.

A triple bond is formed when three pairs of electrons are shared between the two participating atoms. Triple covalent bonds are represented by three dashes (≡) and are the least stable types of covalent bonds.

Example: In the formation of a nitrogen molecule, each nitrogen atoms having five valence electrons provides three electrons to form three electron pairs for sharing.

This type of covalent bond exists where the unequal sharing of electrons occurs due to the difference in the electronegativity of combining atoms. More electronegative atom will have a stronger pull for electrons. The electronegative difference between the atoms is greater than zero and less than 2.0. As a result, the shared pair of electrons will be closer to that atom.

Example: molecules forming hydrogen bonding as a result of an unbalanced electrostatic potential. In this case, the hydrogen atom interacts with electronegative fluorine, hydrogen, or oxygen.

This type of covalent bond is formed whenever there is an equal share of electrons between atoms. The electronegativity difference between two atoms is zero. Nonpolar covalent bonds occur wherever the combining atoms have similar electron affinity (diatomic elements).

Example: Nonpolar Covalent Bond is found in gas molecules like Hydrogen gas, Nitrogen gas, etc.

Properties of Covalent Bond

Some of the properties of covalent bonds are provided below:

• Covalent bonds are very powerful chemical bonds that exist between atoms.
• Covalent bonds do not form new electrons. The bond only pairs them.
• Covalent bonds very rarely break spontaneously after it is formed.
• Covalent bonds are directional where the atoms that are bonded showcase specific orientations relative to one another.
• Most compounds that have covalent bonds have relatively low melting points and boiling points.
• Compounds with covalent bonds usually have lower enthalpies of vaporization and fusion.
• Covalent compounds don’t conduct electricity due to the lack of free electrons.
• Covalent compounds are not soluble in water.

Difference Between Covalent & Ionic Bonds

Aspirants can check the comparison between Covalent Bonds and Ionic Bonds.