How does the empirical formula unit differ from the actual arrangement of ions in an ionic solid?

• A. The empirical formula unit is a molecular formula, while the actual arrangement is an empirical formula.
• B. The empirical formula unit is a 3D structure, while the actual arrangement is a simple ratio of ions.
• C. The empirical formula unit includes all ions, while the actual arrangement includes only cations.
• D. The empirical formula unit represents the simplest ratio of ions, while the actual arrangement is a 3D crystal lattice.

Answer: (D)