A covalent bond is a type of chemical bond that can occur between two atoms or ions in which pairs of electrons are shared with each other. A covalent bond can also be called a molecular bond . Covalent bonds are formed from the union of two atoms that are non-metallic and have identical or relatively close electronegativity values . This type of bond can also be found in other chemical species, such as radicals and macromolecules.. The term covalent bond was first used in 1939, although Irving Langmuir introduced the term “covalence” in 1919, a term he used to describe the number of pairs of electrons shared by neighboring atoms. The pairs of electrons that participate in a covalent bond are called bond pairs or shared pairs . In general, the exchange of bond pairs allows each atom to have an outer shell of electrons which is quite stable, similar to that seen in noble gas atoms.
Covalent bonds are the bonds that are formed between two non-metals and that can share their valence electrons , forming a molecule of several atoms joined together, then they acquire the structure of a noble gas .
- Covalent bond characteristics
- How a covalent bond is formed
- Examples of covalent bonding
Covalent bond characteristics
The main characteristics of covalent bonds are the following:
- Bonds are characterized by the union between two pairs of electrons that are not metals.
- The atoms that join the bond must be able to gain electrons .
- There is a small electronegativity between the atoms.
- They are made up of nonmetals plus nonmetals.
- They have the ability to form molecules
- Covalent bonds are soft when in the solid state .
- They are soluble in water.
- The electrons that are shared are represented by a single line.
- Each electron in the pair that has been shared is attracted to the nuclei of the two atoms.
How a covalent bond is formed
The covalent bond is formed when two of its atoms share one or more pairs of electrons . The difference in electronegativity is responsible for the bond being strong or weak or small.
Depending on the difference in electronegativity , covalent bonds can be classified into two different types, apolar covalent and polar covalent:
- Nonpolar covalent: it is also known by the name of pure or nonpolar covalent bond . It occurs due to the behavior of electrons that occurs between two or more atoms that have the same electronegativity , so its result is 0. They can distribute their electronic charge between the nuclei symmetrically and the electronic pair is attracted by the two cores. When the electronegativity is less than 0.4 it is apolar covalent.
- Polar covalent: this type of bond is a transition that occurs between a pure ionic bond and a covalent bond that is nonpolar . It occurs when there is a compartment of electrons between two or more atoms that have different electronegativity, producing a separation of charges or the distribution of these between the nuclei in an asymmetric way. In this type of bond, different degrees of polarity can occur in the bonds. Its most important characteristic is the degree of symmetry that is determined by the difference between the electronegativity of the atoms.
There are also different types of links, such as:
- Simple bond: it is an electronic pair composed of an electron of the last energy level of each atom and is represented by a line .
- Double bond : it is composed of two shared electronic pairs or two electrons that belong to the last energy level of each atom and is represented by two parallel lines .
- Triple bond : it is formed by three electronic pairs , which means three electrons that belong to the last energy level of each atom and is represented by three parallel lines
- Dative or coordination covalent bond: this bond is an electronic pair shared by two atoms but both electrons are contributed by the same atom.
Covalent bonds can be formed when they are in the liquid state , although they can also appear in the gaseous or solid state . For this reason, they have the property of maintaining their melting and boiling points at normal temperatures. They have the ability to be soluble in solvents that are apolar. They are very poor conductors of electricity and heat . They have two different forces of attraction between the molecules, which is known as the intermolecular force , and this is the reason why their bonds are not so strong.
Examples of covalent bonding
- Methyl Alcohol: CH3OH
- Ethyl Alcohol: C2H5OH
- Propyl Alcohol: C3H7OH
- Methyl Ether: CH3OCH3
- Methylethyl Ether: C2H5OCH3
- Ethyl Ether: C2H5OC2H5
- Formic Acid : HCOOH
- Acetic Acid: CH3COOH
- Propionic Acid: C2H5COOH
- Butyric Acid: C3H7COOH
- Carbon Dioxide: CO2