Covalent bonding takes place when two non-metal atoms bond together. In a covalent bond, one or more pairs of electrons are shared between the two non-metal atoms.
This bonding helps both atoms to achieve a full outer electron shell, which makes them stable. The number of covalent bonds an atom can form is equal to the number of electrons it needs to have a complete outer shell.
Covalent bonds are very strong, which means that a lot of energy is required to break them apart.
Let’s take a look at how covalent bonds form by examining how two different molecules form:
The hydrogen molecule (H2) is formed by two hydrogen atoms bonding together. Each hydrogen atom can only hold a maximum of two electrons, so they need one more electron to achieve a full outer energy level.
To achieve this, two hydrogen atoms react with each other and share their outer electrons. The sharing of electrons results in both hydrogen atoms having a full outer shell. This is what gives the hydrogen molecule its stability.
The chlorine molecule (Cl2) forms when two chlorine atoms bond together. Chlorine is in group 7, which means that it has seven electrons in its outer energy level. To achieve a full outer shell, two chlorine atoms bond with each other by sharing electrons. This forms a single covalent bond.
Only the outer level is involved in the covalent bond, so we did not show the other energy levels. However, this is what the chlorine molecule looks like with all of the energy levels:
A double bond is a type of covalent bond in which two non-metal atoms share two pairs of electrons. This type of bonding is stronger and more stable than a single covalent bond, which only involves one shared pair of electrons.
Let’s look at double covalent bonds in two molecules:
The oxygen molecule (O2) is formed by two oxygen atoms bonding together. Oxygen is in group 6, which means that it has six electrons in its outer energy level.
To achieve a full outer shell, each oxygen atom requires two electrons. To do this, the two oxygen atoms bond with each other by sharing two pairs of electrons. This results in a double covalent bond, in which there are two shared pairs of electrons.
Carbon dioxide (CO2) is a more complex molecule that is formed by a carbon atom bonding with two oxygen atoms. Carbon has four electrons in its outer energy level, so it requires four electrons to achieve a full outer shell. Oxygen, as we discussed earlier, requires two electrons to achieve a full outer shell.
In the formation of CO2, the carbon atom shares two electrons with one oxygen atom and the other two electrons with another oxygen atom. This results in two double covalent bonds, allowing both the carbon atom and the two oxygen atoms to achieve a full outer shell.
Covalent bonds are a type of chemical bond in which two non-metal atoms share one or more pairs of electrons. When two or more atoms bond in this way, they form a covalent molecule. These molecules can be made up of small individual units, or they can form giant, complex molecules.
Simple covalent molecules, such as water (H2O) or hydrogen gas (H2), are made up of a small, fixed number of atoms. Whereas, giant covalent structures, such as silicon dioxide, contain large and variable numbers of atoms.
Although the atoms within a covalent molecule are held together by strong covalent bonds, there are still weak intermolecular forces that exist between individual molecules.