Ionic Bonding

What is an Ionic Bond?

An Ionic bond is an electrostatic force of attraction between oppositely charged ions when electrons are transferred from one atom to another.

An ion is formed when atoms (or groups of atoms) have either lost or gained electrons.

A positive ion (cation) has lost one or more electrons.
A negative ion (anion) has gained one or more electrons.
Ions are extremely small, with cations generally being smaller than their parent atoms and anions larger.

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Example of an ionic bond: Sodium Chloride

Sodium belongs to the alkali metals in Group 1.
Atoms of elements in this group want to lose one electron to have a stable structure.
Chlorine belongs to the halogens in group VII and elements in this group want to gain one electron to have a stable structure.
Therefore, in this bond, the sodium atom $Na$ donates its single outer electron to chlorine.
The $Na$ atom then becomes the sodium ion ( $Na^+$ ), the Cl atom then becomes the chloride ion ( $Cl^-$ ).
The opposite charges attract each other.
This force of attraction holds the ionic bond together as shown in the diagrams below.

The electrostatic force of attraction between sodium and chloride ions is not just one-to-one but occurs in all directions around an ion.

Therefore an ionic compound such as $NaCl$ consists not just of a pair of ions but a network of ions held together in a three-dimensional regular and repeating pattern.
In the case of $NaCl$ , this lattice of ions is a cube as shown in the diagram below

The ionic crystal lattice structure of sodium chloride:

Salt Tablets: Used to replace salt lost during sweating.
Water Softening: Ionic compounds are used to remove calcium and magnesium ions from hard water.