In an ionic bond, ions are held together by the electrostatic force of attraction between positively and negatively charged ions. This force is also known as the Coulomb force. The strength of the ionic bond depends on the charges of the ions and the distance between them. The greater the charges of the ions and the closer they are together, the stronger the ionic bond will be.

For example, the ionic bond between sodium and chlorine in sodium chloride (NaCl) is very strong because the sodium ion has a charge of +1 and the chloride ion has a charge of -1, and the ions are very close together in the crystal lattice.

Ionic bonds are typically formed between a metal and a non-metal. The metal atoms lose electrons to the non-metal atoms, resulting in the formation of positive and negative ions. The ions are then attracted to each other and held together by the electrostatic force of attraction.

Ionic bonds are strong and stable, which is why ionic compounds are typically hard and brittle. Ionic compounds also have high melting points and boiling points.