2.1.2 Ionic Bonding

Ions

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An ion is an atom or a group of atoms that carries a positive or negative charge. Ions are formed when atoms either lose or gain electrons in order to achieve a full outer shell of electrons, which makes them more stable.

Formation of Positive Ions (Cations):

Metal atoms tend to lose electrons from their outer shell.
This loss of electrons results in a positively charged ion because there are more protons (positive charge) than electrons (negative charge).
Example: A sodium atom (Na) loses one electron to form a sodium ion (Na⁺).

Formation of Negative Ions (Anions):

Non-metal atoms tend to gain electrons to fill their outer shell.
This gain of electrons results in a negatively charged ion because there are more electrons (negative charge) than protons (positive charge).
Example: An oxygen atom (O) gains two electrons to form an oxide ion (O²⁻).

Ionic Bonds

Formation:

Ionic bonds form when one atom transfers electrons to another atom. This usually happens between a metal and a non-metal.

Metals tend to lose electrons and become positively charged ions (cations).
Non-metals tend to gain electrons and become negatively charged ions (anions).

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Example: Sodium chloride (NaCl) is formed when sodium (Na) transfers one electron to chlorine (Cl).

\text{Na} \rightarrow \text{Na}^+ + e^-

\text{Cl} + e^- \rightarrow \text{Cl}^-

Bonding:

The positive and negative ions are attracted to each other by electrostatic forces, forming a strong ionic bond. These ions arrange themselves in a regular structure known as a giant ionic lattice.

Properties:

Ionic compounds have high melting and boiling points due to the strong forces of attraction between the ions.
They are usually soluble in water.
Ionic compounds can conduct electricity when melted or dissolved in water because the ions are free to move.

Ionic Bonding Simplified Revision Notes for GCSE Edexcel Chemistry