Electronic Displacement in a Covalent Bond

A covalent bond, also known as the molecular bond, is a chemical bond that is formed when electron pairs are shared between two different atoms. The forces that are present between the two atoms during their bonding, be it attraction or repulsion are termed covalent bonding. To know what is a covalent bond better, here is a simple definition. A covalent bond is an interatomic linkage formed by sharing a pair of electrons between two atoms. After bonding, the total binding energy is lower than vastly separated atoms. Have a look at other details about covalent bonding. 

Covalent bond definition

To begin with, there are a few elements that have high ionization energies. The high ionization energy of the element makes it incapable of transferring its extra electrons to other atoms, ions or molecules. Similar to this, there are a few other elements that have low electron affinity. Meaning they are unfit for receiving electrons from other atoms, ions, or molecules. The atoms of the above type of molecules tend to go through a sharing process. In order to attain stability and complete their octet, these elements undergo electron sharing with the same or different kinds of atoms resulting in covalent bonding. 

Two ways by which covalent bonding can be achieved 

1. Electrons are shared between atoms that are of the same kind. Some examples include the formation process of H2, Cl2, O2, etc. 
2. Electrons are shared between atoms that are of different kinds. Some examples include the formation process of CH4, H2O, NH3, etc. 

Types of covalent bond 

Covalent bonding is categorized into three main types – single covalent bond, double covalent bond, and triple covalent bond. These bonds are divided on the basis of shared electron numbers. Let’s discuss the types of bonding in detail. 

• Single covalent bonds

One of the most common types of covalent bonding is a single covalent bond. During this type of bonding, the two participating atoms share one pair of electrons. One dash (-) represents this type of bonding. Although this type of covalent bonding is weak and has low density yet they are more stable as compared to other types of bonding. An example of a single covalent bond is the HCl molecule. One electron from a hydrogen atom and another electron from seven valence electrons of chlorine have shared that result in a single covalent bond. 

• Double covalent bond 

Another type of bonding is a double covalent bond in which two pairs of electrons are shared between the participating atoms. Two dash lines (=) represent the bonding. However, double covalent bonds are stronger as compared to single bonds, but they are less stable. An example of a double covalent bond is a carbon dioxide molecule. To complete the octet and attain stability, carbon and oxygen share it’s two-two electrons. 

• Triple covalent bond

A triple covalent bond is formed when each participant shares its three electrons with each other. Represented by (≡) lines, this type of covalent bond is least stable. For example, a nitrogen molecule. It is a type when nitrogen contributes three electrons with each other forming a triple covalent bond. 

• Polar covalent bond 

The fourth type of covalent bonding occurs when there is an electronegativity difference between the two atoms. When such a pair shares electrons, the resulting molecule will have an unequal sharing of electrons. An example is when hydrogen bonds with the most electronegativity element, such as fluorine or oxygen. 

• Nonpolar covalent bond 

Non-polar covalent bonding occurs when equal electron sharing between the two participating atoms. Meaning there is no electronegativity difference between them. For example, the nitrogen molecule or hydrogen molecule. 

Electronic displacement in a covalent bond

During covalent bonds, the old bonds between the atoms are replaced by new bonds. The shift or replacement occurs due to the electron shifting. Here are the four types of electronic displacement that occur in covalent bonding. 

Inductive effect:

This permanent effect occurs when an electron-withdrawing or releasing group is attached to the alkane chain. Here is an example – C-C-C-C-C1-X

Suppose if X indicates an electronegative atom. During this formation, X will attract the electron pair towards it, which will establish a negative charge on it. Similarly, C1 will acquire a positive charge due to the shifting of electron pairs. The process continues as C1 will attract the electron pair between C1 – C2. Thus, developing a small positive charge on C2. The chain continues till it becomes zero and diminishes. 

There are two types – +I effect when an electron-withdrawing group is attached and -I effect when an electron releasing group is attached.

Electromeric effect:

Unlike the inductive effect, the electromeric effect is a temporary effect. This effect occurs in the presence of an attacking agent. Represented by multiple bonds, this effect is categorized into two types – +E effect when electrons are shifted to atoms attached to the attacking agent and -E effect when electrons are shifted to atoms other than the atom attached to the attacking agent. 

Resonance:

Resonance occurs in the covalent bond in which π bond electrons are delocalized to get the best structure that is more stable. There are two types of resonance: + R effect when an electron-donating group is attached to the benzene ring and -R effect when an electron-withdrawing group is attached. 

Hyper conjugation:

This is similar to the resonance effect but with one difference. During the hyperconjugation effect, there is no actual bond present between the atoms. There is a condition required in the case that = and – bond must be present at the adjacent positions. This effect in electronic displacement in a covalent bond is also known as Baker Nathan and non-bond resonance. This effect is used to explain the stability of Alkylated alkenes. 

Conclusion 

A covalent bond is formed when two participating non-metallic atoms have similar electronegativity. The bonding that is formed between such bonds has a definite shape and a low melting and boiling point. At room temperature, covalent bonds are in a liquid or gaseous state. In the case of covalent bond sharing formation, the ions formed are polyatomic. Remember, covalent bonds do not form new electrons. Meaning, the bond is formed just by pairing between them. Being a very powerful and strong bond, it has an energy of 80 kilocalories per mole (kcal/mol).