Here's why:
* Ionic bonds are formed by the electrostatic attraction between oppositely charged ions.
* Ions are atoms that have gained or lost electrons, resulting in a net positive or negative charge.
* Formula units represent the simplest ratio of ions in an ionic compound. They are not molecules because they do not involve sharing of electrons.
For example, in sodium chloride (NaCl), the formula unit represents one sodium ion (Na+) and one chloride ion (Cl-). This ratio is the simplest way to express the ionic compound, and it represents the repeating unit in the crystal lattice structure.
