You read about covalent bonds in the article Covalent Bond. You learned what they are and how they are formed. In this article, we shall look at some examples of covalent bonding in molecules, and draw their Lewis structures.
- In this article, we will look at examples of molecules with covalent bonds that we come across in our daily lives.
- We'll see examples of molecules with covalent bonds that the human body interacts with regularly.
- We'll also look at examples of elements that form molecules with covalent bonds, as well as macromolecules with covalent bonds.
- We'll then look at more examples of covalent bonds in simple compounds.
Lewis Structures for Covalent Bonds
Covalent bonds are best represented by drawing Lewis structures. In the article Covalent Bond, you learned to draw the displayed formula of a molecule. Lewis structures can be drawn by showing lone pairs of electrons on each atom in the displayed formula of a molecule.
Lone pairs of electrons are electrons in the outermost shell of any atom that are not participating in any bond formation. They are simply represented by 2 dots.
Lewis structure of water molecule Vaia Originals
This is the Lewis structure of a water molecule, H2O. The lines represent single bonds between hydrogen (H) and oxygen (O) atoms. The two pairs of dots represent two lone pairs of electrons. Now that we know how to draw and read the Lewis structure of any molecule, let's look at some examples of molecules with covalent bonds.
Examples of Covalent Bonding in Everyday Life
We come across substances every day which have molecules with covalent bonding. For example, the air around us is 78% nitrogen gas (N2). We breathe it continuously even though it is not used in respiration at all.
Lewis Structure of Nitrogen | Vaia Originals
Nitrogen has the electronic configuration of [He] 2s2 2p3. It has 5 electrons in its outermost shell. To complete its octet, a nitrogen atom forms a triple bond with another nitrogen atom. This leaves 1 pair of lone electrons on each nitrogen atom.
Carbon Monoxide Covalent Bonding
Your house is probably fitted with a carbon monoxide sensor. Carbon monoxide, CO, is a poisonous gas which is also odourless. This is why sensors need to be installed in houses to detect any leaks. Carbon monoxide is used in boilers.
Lewis Structure of Carbon monoxide with dative bond Vaia Originals
Carbon has the electronic configuration of [He] 2s2 2p2, whilst oxygen has [He] 2s² 2p⁴. Carbon has 4 electrons in its outer shell, and oxygen has 6. By forming a double bond, oxygen completes its octet, but carbon still only has 6 electrons after forming a double bond. So, oxygen donates one of its lone pairs of electrons to carbon, making a coordinate bond / dative bond. The dative bond is represented by the arrow in the Lewis structure.
Chlorine Covalent Bonding
Another example of a substance with covalent bonds is chlorine (Cl2). Do you smell a familiar smell every time you go for a swim in a swimming pool? Chlorine is used as a disinfectant in swimming pools. Chlorine is also used as a bleach and to make pesticides.
Chlorine Lewis Structure | Vaia Originals
Chlorine has the electronic configuration of [Ne] 3s² 3p⁵. It has 7 electrons in its valence shell and only needs 1 more to complete its octet. Therefore, two chlorine atoms form a single covalent bond, and are left with 3 lone pairs of electrons each.
Examples of Covalent Bonding in the Human Body
There are many substances which your body interacts with every second. For example, the oxygen that you breathe is a molecule with covalent bonds.
Lewis Structure of Oxygen | Vaia Originals
You already know that oxygen, O2, has 6 electrons in its outermost shell and needs 2 more to complete its octet. Two oxygen atoms come together to form a double bond and complete their octets. There are 2 lone pairs of electrons on each oxygen atom.
Carbon Dioxide Covalent Bonding
You breathe in oxygen and breathe out carbon dioxide. Carbon dioxide, CO2, is also a molecule with covalent bonds.
Lewis Structure of Carbon Dioxide | Vaia Originals
In the example of carbon monoxide, you saw that oxygen had to donate a pair of electrons to carbon for the octet of carbon to be complete. In a carbon dioxide molecule, carbon forms double covalent bonds with two oxygen atoms. Therefore, there are no dative bonds in carbon dioxide.
Hydrochloric Acid Covalent Bonding
The digestive system of the human body secretes gastric juice to digest food. The gastric juice is highly acidic because a large portion of it is hydrochloric acid (HCl), also called hydrogen chloride.
Lewis Structure of Hydrogen Chloride | VaiaOriginals
Hydrogen chloride is a strong acid and a covalent molecule. You already know that chlorine has 7 electrons in its valence shell, and needs only 1 to complete its octet. Hydrogen has the electronic configuration of 1s1. Recall that the 1s orbital can take only 2 electrons max. Therefore, hydrogen also needs only 1 electron to have a stable electronic configuration. So, hydrogen and chlorine form a single covalent bond.
Examples of Covalent Bonds: Elements
Let us look at some elements that exist as molecules with covalent bonds.
Hydrogen is the first element in the periodic table which exists as a gas with the molecular formula H2. Hydrogen is a highly flammable gas.
Lewis Structure of Hydrogen | Vaia Originals
Hydrogen has only one electron. The outermost orbital of hydrogen is 1s, in which a maximum of 2 electrons can exist. Therefore, hydrogen needs only 1 more electron to have a fully filled outermost electron shell for stability. Therefore, 2 hydrogen atoms form a single covalent bond.
Sulphur Covalent Bonding
The molecule of sulphur is rather interesting. Elemental sulphur exists as S8, forming a crown-like structure.
Lewis Structure of Sulphur | Vaia Originals
Sulphur has the electronic configuration of [Ne] 3s² 3p⁴. It has 6 electrons in its outermost shell and needs 2 more to complete its octet. You must be wondering - why doesn't sulphur form a diatomic molecule S2 as oxygen does. That is because Sulphur usually doesn't form a double bond with itself because of its large atomic radius.
Phosphorus Covalent Bonding
Phosphorus has the atomic number 15 on the periodic table. its electronic configuration is [Ne] 3s² 3p³ . White phosphorus exists as a tetrahedral structure with the chemical formula P4.
Lewis Structure of White Phosphorus | Vaia Originals
A tetrahedral structure is that of a pyramid. Can you see a pyramid in the Lewis structure for phosphorus drawn above? White phosphorus is highly flammable, and is used in fireworks, and in ammunitions for the military.
White phosphorus is so flammable that it catches fire spontaneously in the air i.e., without the aid of any spark or heat.
Examples of Covalent Bond: Compounds
Now let us look at some other examples of molecules with covalent bonding.
Methane is a hydrocarbon with 1 carbon atom, which forms the majority of natural gas. Methane is also a greenhouse gas, which means it affects the temperature of the Earth's atmosphere.
Hydrocarbons are molecules that are made up of carbon and hydrogen atoms only.
Lewis structure of Methane Vaia Originals
We already know that carbon needs 4 electrons to have a stable electronic configuration, and that each hydrogen atom needs 1 electron to achieve the same. So, a carbon atom forms 4 single bonds with 4 hydrogen atoms and methane is formed. There are no lone pairs of electrons on any atom.
Ethane Covalent Bonding
Ethane is another hydrocarbon but it has 2 carbon atoms. The molecular formula of ethane is C2H6.
Lewis Structure of Ethane | Vaia Originals
To draw the lewis structure of ethane, just replace one of the hydrogens of methane and replace it with another carbon atom, and complete the octet of this carbon by forming bonds with more hydrogen atoms.
Ethene Covalent Bonding
Now let us look at a different kind of hydrocarbon - ethene. Notice the spelling difference between ethane and ethene. Ethene is a hydrocarbon with carbon atoms sharing a double bond. The molecular formula is C2H4.
Lewis Structure of Ethene with Double Bond between Carbon Atoms | Vaia Originals
The octet of carbon is still being fulfilled (4 covalent bonds per carbon atom).
Remember that double bonds are shorter than single bonds. Carbon atoms bonded with a double bond are more closely held together than carbon atoms sharing a single bond.
Ammonia Covalent Bonding
Ammonia is a weak base. The chemical formula is NH3. It is used in the production of fertilisers, pesticides, textiles, explosives and many other things. It is also used as a refrigerant gas.
Lewis Structure of Ammonia | Vaia Originals
As we saw in the example of N2, each nitrogen atom is left with a lone pair of electrons after forming 3 covalent bonds. In ammonia, these 3 covalent bonds are formed with 3 hydrogen atoms.
Ammonia reacts with a water molecule (H-OH) to form the ammonium ion by donating its lone pair of electrons to an H+ ion. In doing so, a positive charge is acquired by the ion.
Lewis Structure of Ammonium Ion with Dative Bond | Vaia Originals
The donated pair of electrons forms a dative bond between the nitrogen and the hydrogen atom.
Aluminium Chloride Covalent Bonding
Let us look at another example of a molecule with a dative bond. Aluminium chloride, the chemical formula for which is AlCl3, actually exists as Al2Cl6. (Notice that aluminium and chlorine are present in the same ratio 1:3 in both formulas.) Let us look at the Lewis structure to understand why this is so.
Dative Bonds Between Two AlCl3 Molecules, forming Al2Cl6 | Vaia Originals
The Lewis structure of Al2Cl6 is seen as two molecules of AlCl3. Below is a molecule of AlCl3.
Lewis Structure of Aluminium Chloride, AlCl3 | Vaia Originals
The electronic configuration of aluminium is [Ne] 3s² 3p¹. It has 3 electrons in its outermost shell, which are shared to form single covalent bonds with 3 chlorine atoms in AlCl3. But the aluminium atom is still short of 2 electrons to complete its octet. Therefore, aluminium accepts an electron pair from the chlorine atom of another AlCl3 molecule. The aluminium in that molecule also accepts an electron pair from this AlCl3 molecule.
Examples of Covalent Bonds: Macromolecules
Macromolecules are very large molecules consisting of millions of atoms. These molecules are usually made up of repeating units of some basic structure. Let us look at some examples to understand this better.
Graphite Covalent Bonding
Graphite is an example of a macromolecule composed of only carbon atoms. In graphite, each carbon atom forms covalent bonds with 3 other Carbon atoms.
Since graphite is composed completely of carbon, it is called an allotrope of carbon.
Graphite structure,TOSAKA, public domain , Created using images from Wikimedia Commons
In the figure of graphite, you can clearly see how each carbon atom forms a covalent bond with 3 other carbon atoms. The solid lines you see in the figure represent these bonds. They form layers of these structures.
By forming only 3 bonds instead of 4, carbon has a free electron. This unpaired electron is delocalised over the whole structure of graphite i.e., it is not associated with any particular atom and is free to move around. Due to these free-moving electrons, graphite is a good conductor of electricity. You can check this yourself by making an electric circuit out of your pencil leads right now!
Despite the 4th electron being delocalised, they form weak intermolecular bonds with adjacent layers. The dotted lines you see between the layers of rings represent these weak intermolecular bonds.
You can read more about graphite in this article.
Diamond Covalent Bonding
Diamond is a mineral that is completely made up of carbon atoms. Each carbon atom forms single covalent bonds with 4 other carbon atoms.
Like graphite, diamond is also an allotrope of carbon.
The structure of diamond, Public domain, Wikimedia commons
Diamond is the hardest material in the world thanks to its structure. This structure is called a tetrahedron. The tetrahedral structure of diamond is like a triangular pyramid with a carbon atom on each of the pyramid's corners and one atom in the centre.
Recall that atoms of white phosphorus are also arranged in a tetrahedral geometry. But don't confuse the two - the bonding between atoms is completely different in phosphorus and diamond!
Besides jewellery, diamond is also used in industrial tools such as drill bits, abrasive materials used in grinding wheels etc, polishing cloth/paste and many more applications. The fact that it is the hardest material in the world means that it can be used to cut, grind, or polish anything.
Examples of Covalent Bonding - Key takeaways
- In this article, we saw many examples of molecules with covalent bonding.
- Examples of molecules with covalent bonds that we interact with every day.
- Examples of molecules with covalent bonds that the human body interacts with every day.
- Examples of elements that exist as molecules with covalent bonds.
- Examples of other small compounds with covalent bonds.
- Examples of macromolecules with covalent bonds
Explanations 
Textbooks 
Exams 
Magazine 
