The word covalent is normally used to designate a type of bond that occurs between the electrons of different atoms. The covalent bond represents the sharing of (negative) electrons at a level that, however, is not enough to speak of electron exchange between the two atoms. These bonds between electrons fall within the realm of chemical science.
The covalent bond can be described, in other words, as the bond that is established between the electrons of different atoms and that generates the attraction-repulsion phenomenon that occurs between them. This phenomenon (or covalent bond) is what maintains the stability between these atoms thus united through their electrons.
It is estimated that the term "covalent bond" began to be used in the early 20th century, more specifically in 1919, by Irving Langmuir. This scientist used the notion of covalent to designate those pairs of electrons shared by an atom with its neighboring atoms. The union of electrons between atoms can be simple (when one is shared), double or triple and thus form more or less complex substances according to the number of electrons and atoms that are related to each other.
Covalent bonds can give rise to two types of substances or main materials: those that are soft when in solid state, are insulators of electrical energy, can be found in all three states (liquid, gaseous and solid) and that have boiling ranges. and melt low compared to other substances. These substances are called "molecular covalent substances." The second group is made up of substances that are only solid, are not soluble in any liquid or substance, have high melting and boiling temperatures and are also insulating. We know them as network substances. Furthermore, these network substances are always very harsh.
