Covalent Bond

A covalent bond is a chemical bond formed by the sharing of electron pairs between two or more atoms in a compound.This stable balance of attractive and repulsive forces between atoms, when they share electrons, is referred to as covalent bonding.When two atoms share electrons, they form shared pairs, which are referred to as bonding pairs. For many molecules, the sharing of electrons allows each atom to achieve the equivalent of a full valence shell, which corresponds to an electronic configuration that is stable under standard conditions. Covalent bonds are much more common in organic chemistry than ionic bonds, which is a good thing.

Additionally, covalent bonding encompasses many different types of interactions.These include the following types of interactions: alpha and beta atom bonding, alpha and beta atom bonding, metal-to-metal bonding, agostic interactions (also known as bent bonds), three-centre two-electron bonds, and three-centre four-electron bonds.

The term “covalent bond” was first used in 1939.

The prefix co- denotes that the atoms are acting together, that they are associated in action, that they are partnered to a lesser degree, and so on; a “covalent bond” denotes that the atoms are sharing “valence,” as discussed in valence bond theory.

Covalent bonding allows the hydrogen atoms in the molecule H2 to share the two electrons between themselves.

The degree of covalency between atoms with similar electronegativities is the greatest. Consequently, covalent bonding does not necessitate that the two atoms belong to the same element, but rather that they have electronegativity values that are comparable.Delocalized covalent bonding is defined as covalent bonding that involves the sharing of electrons between more than two atoms.

History

It was Irving Langmuir who coined the term “covalence” to refer to the arrangement of electrons in atoms and molecules in his 1919 Journal of the American Chemical Society article entitled “The Arrangement of Electrons in Atoms and Molecules.” The term “covalence” refers to the number of pairs of electrons that a given atom has in common with its neighbours, according to Langmuir.

Gilbert N. Lewis, who published a paper in 1916 describing the sharing of electron pairs between atoms, is credited with originating the concept of covalent bonding several years before 1919.

Lewis devised the Lewis notation, also known as electron dot notation or Lewis dot structure, in which valence electrons (those in the outer shell) are represented as dots around the atomic symbols, which is still in use today. Covalent bonds are formed by electron pairs that are located between two atoms. Multiple bonds, such as double bonds and triple bonds, are represented by multiple pairs of atoms. Bond-forming electron pairs are represented as solid lines in an alternate form of representation, which is not shown in this example.

Lewis proposed that an atom can form enough covalent bonds to form a full (or closed) outer electron shell by forming enough covalent bonds. The carbon atom in the diagram of methane shown here has a valence of four and is, as a result, surrounded by eight electrons (the octet rule), four from the carbon atom itself and four from the hydrogens that are bonded to it (see figure below). One electron surrounds each hydrogen atom, which has a valence of one and is surrounded by two electrons (a duet rule) – its own one electron plus one from the carbon atom surrounding it. Atomic shells are represented by numbers of electrons; the outermost shell of a carbon atom is denoted by the n = 2 shell, which can hold eight electrons, whereas the outermost (and only) shell of a hydrogen atom is denoted by the number 1, which can hold only two electrons.

The Characteristics of a Covalent Bond

Whenever the normal valence of an atom cannot be satisfied by the sharing of a single electron pair between atoms, the atoms may choose to share more than one electron pair between them instead. The following are some of the characteristics of covalent bonds:

•Because of the nature of covalent bonding, it does not result in the formation of new electrons. They are only linked together by the bond.

•They are chemical bonds that exist between atoms that are extremely powerful.

•A covalent bond typically contains about 80 kilocalories per mole (kcal/mol) of energy, which is considered to be a significant amount.

•Covalent bonds are extremely rare to break spontaneously after they have been formed.

•Covalent bonds are directional in nature, meaning that the atoms that are bonded have specific orientations in relation to one another when they are joined.

•The melting and boiling points of the vast majority of covalently bound compounds are relatively low in comparison to other compounds.

•Compounds with covalent bonds typically have lower vaporisation and fusion enthalpies than other types of compounds.

•Compounds formed through covalent bonding do not conduct electricity due to the absence of free electrons in the compound.

•Covalent compounds are not soluble in water and must be dissolved in acid.

Polar Covalent Bonds

It is possible to form this type of covalent bond when the unequal sharing of electrons occurs as a result of the difference in the electronegativity of the combining atoms’ electronegativity. An atom that is more electronegative will have a stronger pull on electrons. More than zero and less than 2.0 are present in the electronegative difference between the atoms. As a result, the shared pair of electrons will be closer to the atom in question than previously thought.

As an illustration, consider the formation of hydrogen bonds between molecules as a result of an unbalanced electrostatic potential. In this instance, the hydrogen atom interacts with electronegative elements such as fluorine, hydrogen, or oxygen to form a compound.

Nonpolar Covalent Bond 

Whenever there is an equal share of electrons between two atoms, a type of covalent bond is formed between them.The difference in electronegativity between two atoms is equal to zero.It occurs whenever the combining atoms have electron affinities that are similar (diatomic elements).

For example, nonpolar covalent bonds can be found in gas molecules such as hydrogen gas, nitrogen gas, and other similar gases.

Conclusion

A covalent bond is a chemical bond formed by the sharing of electron pairs between two or more atoms in a compound.This stable balance of attractive and repulsive forces between atoms, when they share electrons, is referred to as covalent bonding.It was Irving Langmuir who coined the term “covalence” to refer to the arrangement of electrons in atoms and molecules in his 1919 Journal of the American Chemical Society article.Whenever the normal valence of an atom cannot be satisfied by the sharing of a single electron pair between atoms, the atoms may choose to share more than one electron pair between them instead.Whenever there is an equal share of electrons between two atoms, a type of covalent bond is formed between them.The difference in electronegativity between two atoms is equal to zero.