Final answer:
The chemical formula for an ionic compound represents a formula unit, embodying the simplest whole-number ratio of the ions that makes the substance electrically neutral.
Step-by-step explanation:
The chemical formula for an ionic compound represents one formula unit. A formula unit refers to the simplest whole-number ratio of the ions comprising the compound, which maintains electrical neutrality. An example of this is sodium chloride, in which the formula NaCl implies a 1:1 ratio of sodium ions (Na+) to chloride ions (Cl−), creating an electrically neutral compound.
Ionic compounds are made up of a lattice of cations and anions, not discrete molecules. Hence, the formula does not represent a single molecule or a specific cation or anion, but rather the proportion of each ion in the crystal lattice. For instance, in aluminum oxide (Al2O3), there are two aluminum cations (Al3+) for every three oxide anions (O2−), which reflects the necessitated balance of charges.