Bonding

So far, we have learnt that protons, neutrons and electrons can join together to form larger particles called atoms and ions.

Atoms and ions can also join together to form even larger particles. Atoms can join together with other atoms, and ions can join together with other ions. This is called bonding.

Most of the chemical substances (solids, liquids and gases) that we encounter in our lives are made up of atoms or ions bonded together into larger particles.

There are three types of bonding

There are three different types of bonding, called covalent bonding, ionic bonding and metallic bonding.

Covalent bonding takes place between atoms, whereas ionic and metallic bonding both take place between ions.

In each type of bonding, the atoms or ions are held together in a different way. However, the electrostatic force is always involved.

In covalent bonding, a pair of electrons is shared between two atoms. It is electrostatic attraction between the negatively charged electrons and the positively charged nuclei that holds the atoms together.

In ionic bonding, cations and anions are bonded together. Because they have opposite charges, there are forces of electrostatic attraction that hold them together.

In metallic bonding it is just cations that are bonded together. The cations are surrounded by a sea of electrons that are delocalised (free to move between the ions). It is electrostatic attraction between the positively charged ions and the negatively charged sea of delocalised electrons that holds the ions together.

Each type of bonding will be explained in detail later in the chapter. For now, the key features of each type are summarised in the table below:

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