Bonding is an essential part of our world. Without it, atoms would just float around without interacting with each other, and we wouldn't have the molecules and compounds that make up everything around us. Imagine a world without bonding - the water in the ocean would just split into hydrogen and oxygen gases, and chlorine atoms from salts in the water would form a toxic cloud. Not a very pleasant place to live, right?

Bonding happens when different atoms interact to form compounds, molecules, ions, crystals, and all the other substances that make up our world. It's caused by the attraction between positive and negative charges. There are two categories of bonding - primary and secondary. Primary bonding happens between atoms within a molecule and is generally strong and hard to break. Secondary bonding, on the other hand, happens between molecules and is a lot weaker.

In conclusion, bonding is what makes our world possible. Without it, we wouldn't have the chemistry that makes life as we know it possible. So next time you see a molecule or compound, remember that it's only there because of bonding. And if you're interested in learning more about bonding, be sure to check out our other articles on the topic!

Why do bonds form?

Atoms crave stability - they prefer to be in a low energy state. They can achieve this by bonding with other atoms in different ways to form various substances.

The stability of an atom depends on the number of electrons in its outer shell. To reach maximum stability, an atom needs a full outer shell of electrons, like noble gases. Noble gases are already as stable as they can be, which is why they don't bond with other atoms. They exist as monatomic gases.

A monatomic substance is a substance that consists of only one atom. Instead of bonding with other atoms, each atom floats around independently.

When atoms bond together, they form molecules or compounds. A molecule is created when two or more atoms are chemically bonded together. If the atoms come from two or more different elements, then the molecule is called a compound.

In summary, atoms seek stability, and they can achieve this by bonding with other atoms to form various substances such as molecules and compounds. Noble gases are already stable, so they exist as monatomic gases.

Types of bonding

We mentioned above that bonding occurs because of attraction between positive and negative charges. You should know from Atomic Structure and Fundamental Particles that atoms are made up of protons, neutrons, and electrons. The table below summarises their charges and locations within the atom.

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You can see that protons have a positive charge and electrons have a negative charge. These are the only charged particles within an atom. All attraction, and therefore all bonding, must be between protons and electrons. We know that atoms try to form bonds in order to achieve a full outer shell of electrons. They do this by moving their electrons around between each other. They can do this in three different ways, which result in three different types of bonding:

Sharing electrons results in covalent bonding. Donating electrons results in ionic bonding. Delocalising electrons results in metallic bonding.

Covalent bonding

Covalently bonded atoms share electrons with each other so that they all have full outer shells of electrons.

A covalent bond is a shared pair of electrons.

Only non-metals form covalent bonds. Electron orbitals from two different atoms overlap, and a shared electron pair is formed using an electron from each atom. The bond is held together by the attraction between the negative shared electron pair and the positive nuclei inside the two atoms.

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Ionic bonding

Ionic bonding occurs between metals and non-metals. Ionic bonds are formed when a metal atom donates electrons to a non-metal. This forms charged atoms known as ions, which are attracted to each other. An ionic bond is an electrostatic attraction between oppositely charged ions.

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Metallic bonding

For a metal on its own to have a full outer electron shell, it must do something quite different. Its outer electrons delocalise and the metal forms positive metal ions. Unlike in ionic bonding, where the electrons are picked up by another atom, in metallic bonding the electrons float about freely within the structure. The attraction between the negative electrons and the positive metal ions holds the metal together. A metal bond is the electrostatic attraction between delocalised electrons and positive metal ions.

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Intermolecular forces

As you now know, substances made from two or more atoms joined together by chemical bonds are called molecules. For example, two hydrogen atoms and one oxygen atom bond to form a water molecule. We know that bonds are found within molecules. What forces are found between molecules?

The answer is Intermolecular Forces, which can also be known as secondary bonds. There are three different types: Van der Waals forces.Permanent dipole-dipole forces. Hydrogen bonding.

Van der Waals forces

Van der Waals forces are the weakest type of intermolecular force. They occur between all molecules. The random movement of electrons within a molecule causes a temporary dipole, which induces a dipole in a neighbouring molecule. The attraction between the two dipoles holds the molecules together.

Permanent dipole-dipole forces

In some molecules, the electrons are permanently distributed in an uneven manner. This means that one side of the molecule is constantly more negative than the other, and we call this a permanent dipole. Oppositely charged dipoles attract each other. The forces are known as permanent dipole-dipole forces and are stronger than van der Waals forces.

Hydrogen bonding

Some molecules that contain hydrogen atoms can experience an even stronger type of intermolecular force called hydrogen bonding. This bonding occurs between molecules that have a hydrogen atom bonded to an oxygen, nitrogen, or fluorine atom.

The diagram below shows the different types of primary and secondary bonds, also known as intramolecular and intermolecular forces, ranked according to their strength. Although hydrogen bonds are the strongest type of intermolecular force, they are still much weaker than intramolecular forces such as covalent, ionic, and metallic bonds. For a more in-depth understanding of the various types of bonding and forces, feel free to explore our articles on Covalent Bond, Ionic Bonding, Metallic Bonding, and Intermolecular Forces.

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Bonding and structure

Just by looking at everyday objects around us, it's easy to see that different types of bonding produce very different types of structures. For instance, a diamond ring is made up of metal that is easily shaped into a circular torus, while the diamond embedded in the centre is extremely hard and strong. Diamond doesn't even melt under normal atmospheric conditions and instead sublimes into a gas at extremely high temperatures.

This is because metals bond using metallic bonds, while diamond uses covalent bonds, which give the two substances very different structures and properties. However, oxygen is also a covalent molecule, yet it behaves completely differently from diamond. For example, oxygen is a gas at room temperature, while diamond requires extreme temperatures before it sublimes. Therefore, we can deduce that a molecule's properties are not only affected by the type of bonding but also the structure and arrangement of atoms, as well as how the bonds hold the molecule together. The table below provides a summary of the different types of structures found in chemistry.

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Bonding and shape

In addition to metals and ionic substances, some covalent substances also form lattices. A lattice is a regularly repeating arrangement of atoms or molecules. For example, the ionic lattice of sodium chloride alternates positive sodium ions and negative chloride ions. However, a simple covalent molecule doesn’t have a lattice structure. Instead, it forms a molecule with a specific shape, depending on the number of electron pairs and covalent bonds it contains.

The shape of a molecule is determined by its electron pairs. Imagine two magnets with the same poles near each other. They will try to separate because similar charges repel each other. Electron pairs are similar in that they try to spread out as far apart as possible. If all electron pairs are part of covalent bonds, the bonds will be equally spaced apart. However, lone pairs, which are electron pairs that aren't part of a bond, have a stronger repulsive force than bonded pairs. They repel other electron pairs more and push the bonded pairs closer together.

For example, methane (CH4) has four electron pairs in its outer shell, all of which are bonded pairs that repel each other equally. The angle between each of the bonded pairs is 109.5°. In contrast, water (H2O) also has four electron pairs in its outer shell, but two of the pairs are lone pairs, which squashes the bond angle to just 104.5°.

The table below summarizes the shapes of different covalent molecules, along with diagrams to help consolidate your knowledge.

Bonding - Key takeaways

Bonding is the interaction between different atoms that results in the formation of molecules, compounds, and all other substances that make up the everyday world around us. Atoms bond in order to achieve a more stable energy state. This usually happens by moving electrons about to achieve a full outer electron shell, like that of a noble gas. Primary bonds are also known as intramolecular forces and occur within molecules. They are much stronger than secondary bonds, also known as intermolecular forces, which occur between molecules. The three types of primary bonding are covalent, ionic, and metallic bonding.

Covalent bonding occurs when atoms share electrons in order to complete their outer electron shells. This type of bonding is generally found in non-metallic elements and compounds. Ionic bonding occurs when one or more electrons are transferred from one atom to another, resulting in the formation of positively and negatively charged ions. This type of bonding is typically found in metallic and non-metallic elements and compounds. Metallic bonding is found in metals and is characterized by the free movement of electrons within a lattice of positive ions.

Secondary bonding, on the other hand, occurs between molecules and is much weaker than primary bonding. The three types of secondary bonding are van der Waals forces, permanent dipole-dipole forces, and hydrogen bonding. Van der Waals forces are the weakest of the three and occur between non-polar molecules. Permanent dipole-dipole forces occur between polar molecules and are slightly stronger than van der Waals forces. Hydrogen bonding occurs when a hydrogen atom is bonded to a highly electronegative atom, such as oxygen, nitrogen, or fluorine, and is the strongest type of secondary bonding. Bonding influences a molecule or compound’s shape, structure, and properties. The type of bonding and the arrangement of atoms within a molecule or compound can impact its physical and chemical properties, such as boiling point, melting point, conductivity, and reactivity. Understanding bonding is key to understanding the behavior of matter at the atomic and molecular levels.

Bonding

What is a chemical bond?

A chemical bond is the interaction between different atoms to form a molecule or compound, due to lasting attraction between positive and negative charges.

What is a covalent bond?

 A covalent bond is a shared pair of electrons.

What is an ionic bond?

An ionic bond is the electrostatic attraction between oppositely charged ions.

What is a metallic bond?

A metallic bond is the electrostatic attraction between positive metal ions and delocalised electrons.

How are covalent bonds formed?

Covalent bonds are formed when atoms share a pair of electrons. Each atom provides one electron from its outer shell, which join to form a shared pair.

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