Since the beginning of studies regarding the characteristics of matter, scientists intuited the existence of a force capable of establishing links between different species. "Particles are attracted to each other by forces" was what Isaac Newton said, and years later, thanks to the invention of the famous voltaic pile, Jöns Jakob Berzelius, would develop a theory regarding the chemical combination process.
Thanks to the progress of the study carried out by various scientists, today we have the certainty that chemical elements, like human beings, interact with each other, and from this action derive new structures, fusions, among other processes.
The result of such interaction depends on the individual characteristics of each participant, which will limit the type of union produced, among others. So that within a molecule a nonpolar covalent bond occurs the species involved must be very similar in terms of electronegativities.
Conditions that determine the formation of links
Although it can be thought that these processes of formation of compounds through the creation of bonds, occur spontaneously, and in all possible scenarios, the truth is that the union between atoms of elements occurs when the surrounding conditions of the process are favorable, which It means that factors such as temperature and pressure, are limiting of the occurrence, and also alter the result or the characteristics of the compound formed.
Another important aspect is the concentration of the substances, which determines what amount and what type of component will result from the combination process.
The individual characteristics of the particles, which are what establish in what quantity and which species are combined; determining in the same way the type of link to develop. We must remember that, according to Pauling's rule, the type of bond formed will depend on the electronegative difference between the species, which according to their scale:
- Ionic: Difference greater than or equal to 1,7. This shows that this type of bond is characteristic in kind with very different electronegativities, so that the most electronegative atom donates electrons from its last shell.
- Covalent: Difference between 1,7 and 0,5. It is said that it is usually formed between elements of high electronegativity (non-metals), and it happens that the compound formed is the result of the compartment of atoms.
- Non-polar: It happens when the recorded difference is less than 0,5 (although it is usually equal to zero).
What is a nonpolar covalent bond?
A bond a way of defining the bonding process between two or more atoms, as a product of the attractive forces generated. As is well known, the nucleus of atoms is positive in character (since it is made up of protons and neutrons), for this reason the natural tendency of two chemical species is to repel each other, however, it is the electron cloud that orbits around the nucleus which makes possible the process of formation of chemical bonds.
For a bond to occur, the chemical species present must present the following general characteristic:
One of them must show a lack of electrons in its last shell, and the other must have available electronic charge to share. This attraction situation makes it impossible for the repulsion force between nuclei to be canceled due to its magnitude of unifying force.
A nonpolar covalent bond, is the action that unifies atoms that have a very similar nature, since their occurrence is determined by a difference in electronegativities that tends to 0 (or as established by Linus Pauling: in an interval less than 0,5). The molecules resulting from this type of union do not have an electric charge and are symmetrical in their structure. It is not a type of link that occurs frequently, however, among the examples of this type of union we can mention:
- Links between two or more species of the same atom: If you are dealing with the union between two equal species, the electronegativity difference will be zero, therefore, a species with a nonpolar covalent bond would be defined.
- Methane is an exceptional case, in which, for the similar electronegativity between carbon (C) and oxygen (O2), the difference is 0,4.
- Some species whose states of aggregation are diatomic, such as hydrogen (H2), nitrogen (N2), fluorine (F2) and oxygen (O2) tend to form this type of junction. These types of species tend to be coupled in pairs, since they require another molecule to be chemically stable.
Characteristics of compounds with nonpolar covalent bonds
- They have low melting and boiling points.
- They do not conduct heat well.
- They are insoluble in water at various temperatures.
- They are poor conductors of electricity, they are molecules with a neutral electric charge.
- The molecules are symmetric with respect to a reference plane in a perpendicular position between the two nuclei.
Procedure to identify the type of bond in a molecule
If you want to identify more precisely if the type of bond in a molecule is nonpolar covalent type, you must follow the following simple steps, to perform the verification mathematically:
- First of all, you must identify what type of elements make up the molecule and their nature: if they are metals, you can locate their electronegativity on the left side of the periodic table, and if they are non-metallic on the right side.
- Before doing the calculation, you can already have a notion about the result you are going to obtain, since, by definition, if you are in the presence of two non-metallic elements, a covalent bond will form.
- You locate the electronegativities of each species on the periodic table of the elements.
- You perform a simple subtraction, and then you place in the table the type of link to which your result corresponds.
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