An Idea on Non-polar Covalent Compounds

What Is A Covalent Bond?

When two or more similar atoms combine, the process of gaining or losing electrons cannot take place between them. In such a scenario, a bond forms due to the mutual sharing of electron pairs. The force which binds similar atoms of the same or different elements with the help of the mutual sharing of electrons is known as a covalent bond.

Atoms involved in a covalent bond formation contribute an equal number of electrons to share. The shared electron pairs, also called a bond pair of electrons, become a common entity of both the atoms to form a bond between them. Common examples exhibiting covalent bonds are H2O, Cl2, NH3, etc.

Cl2 molecule: Cl-Cl

An easy method of identifying the presence of a covalent bond in a given molecule is when there are only non-metals or a combination of non-metal and semimetal in a molecule. For example, in covalent compounds such as H2O and SiO2, H and O both are non-metals. In SiO2 (silicon dioxide), Si is a semimetal, whereas O is a non-metal.

Types Of Covalent Bonds: 

1. Single covalent bond: In cases where only one electron pair is being shared between two atoms. Examples: CCl4 (Carbon tetrachloride), NH3 (Ammonia), Cl2, H2O, etc.
2. Double (covalent) bond: In cases where two electron pairs are being shared between two atoms. Examples: CO2 (Carbon dioxide), O2, C2H4 (Ethene), etc. 
3. Triple (covalent) bond: In cases where three electron pairs are being shared between two atoms. Examples: N2, C2H2 (Ethyne), etc.

Coordinate-Covalent Bond/ Dative Bond: There is a special case of covalent bond formation in which though two atoms mutually share the electron pair, the electron pair is contributed only by one of the atoms, and the other atom participates in sharing. The atom which donates electron(s) is called the donor, and the other receiving atom is called the acceptor.

Here, the donor must have already completed its octet, while the acceptor accepts the electron pairs in order to complete its octet. The bond is represented by an arrow (→ ) pointing from the donor to the acceptor. Examples: O3 (Ozone), SO2 (Sulphur dioxide), NH4+  (Ammonium ion), HNO3 (Nitric acid), etc.

Polarity Of Covalent Bonds

Non-Polar Covalent Bond

The electron pair shared between two atoms is equally attracted by the two atoms in a covalent bond. As a result, the shared electron pair lies exactly between the two atomic nuclei. The bond polarity is directly proportional to the electronegativity difference between the two atoms. Due to the similarity of the atoms, the electronegativity difference between the atoms is zero. The electron cloud surrounding the molecular orbital is symmetrical. Examples of nonpolar covalent compounds are H2, O2, N2, F2, etc.

Representation: A: A or A-A. Here, (:) represents the shared electron pair between the two atoms according to the Lewis dot structure.

Polar Covalent Bond

If a covalent bond is formed between two dissimilar atoms, with one having a larger electronegativity value than the other, the electron pair gets displaced towards the more electronegative atom. The electron cloud containing the bonding electrons gets distorted, and the charge density concentrates more around the electronegative atom.

Due to the unequal distribution of electron charge density, the more electronegative atom acquires a partial negative charge ( –), and the less electronegative atom acquires a partial positive charge ( +). Thus, this type of covalent bond develops a partial ionic character due to the differences in electronegativities of the atoms comprising the bond. An example of a polar covalent compound is HCl.

Representation: A: B or  A ( +)-B ( -)

Conclusion

In this article, we saw an overview of covalent bonding and some covalent compounds. A covalent bond is formed by the mutual sharing of electron pairs, in which both the involved atoms contribute equally. Moving further, we saw the different types of covalent bonds on the basis of bond number. A unique type of covalent bond mentioned is the dative bond, in which only one atom (donor, more electronegative) contributes to the sharing of the electron pair, whereas the other atom (acceptor, less electronegative) which only participates in electron pair sharing. We also discussed the two types of covalent bonds on the basis of polarity: non-polar and polar covalent bonds, along with their examples.