Covalent Link: Concept, Types and Examples

We explain to you that it is a covalent bond and some of its characteristics.In addition, the types of covalent bond and examples.

In a covalent bond, the linked atoms share a pair or more of electrons.

What is a covalent bond?

A type of chemical bond is called covalent bonding, which occurs when two atoms bond to form a molecule, sharing electrons belonging to its most superficial layer, thereby reaching the well-known "stable octet" ( according to the "octet rule" proposed by Gilbert Newton Lewis on the electrical stability of atoms).The atoms thus linked share a pair (or more) of electrons, whose orbit varies and is called molecular orbital .

Covalent bonds are different from ionic bonds, in which an electron transfer occurs and that occur between metallic elements.The latter, in addition, form electrically charged molecules, called ions: cations if they have a positive charge, anions if they have a negative charge.

Instead, certain covalent bonds (between different atoms) are characterized by an electronegativity concentration.in one of the two atoms together, since they do not attract with the same intensity the cloud of electrons around them.This results in an electric dipole, that is, a molecule with positive and negative charge at its ends, like a battery ordinary: a positive and a negative pole.Thanks to this the covalent molecules join with similar ones and form more complex structures .

It can serve you: Metal Link.

Covalent link types

In a double bond the linked atoms contribute two electrons each.

There are the following types of covalent bond, from the number of electrons shared by the linked atoms:

• Simple.The linked atoms share a pair of electrons from their last layer (one electron each).For example: H-H (Hydrogen-Hydrogen), H-Cl (Hydrogen-Chlorine).


• Double.The linked atoms provide two electrons each, forming a bond of two pairs of electrons.For example: O=O (Oxygen-Oxygen), O=C=O (Oxygen-Carbon-Oxygen).


• Triple.In this case the linked atoms provide three pairs of electrons, that is, six in total, for example: N≡N (Nitrogen-Nitrogen).


• Dative.A type of covalent bond in which only one of the two atoms linked provides two electrons and the other, however, none.

On the other hand, according to the presence or not of polarity, one can distinguish between polar covalent bonds (which form polar molecules) and non-polar covalent bonds (which form non-polar molecules):

• Polar covalent bonds.Atoms of different elements are linked and with electronegativity difference above 0.5.This is how electromagnetic dipoles form.


• Non-polar covalent bonds.Atoms of the same element or identical polarities are linked, with a very small electronegativity difference (less than 0.4).The electronic cloud is thus attracted with equal intensity by both nuclei and a molecular dipole is not formed.

Examples of covalent bonding

Pure nitrogen (N2) has a triple bond.

Simple examples of covalent bonding are those given in the following molecules:

• Pure oxygen (O2).O=O (a double bond)


• Pure hydrogen (H2).H-H (a simple link)


• Carbon dioxide (CO2).O=C=O (two double bonds)


• Water (H2O).H-O-H (two simple links)


• Hydrochloric acid (HCl).H-Cl (a simple link)


• Pure nitrogen (N2).N≡N (a triple link)


• Cyanhydric acid (HCN).H-C≡N (a single and a triple link)