Final answer:
The empirical formula represents the simplest ratio of elements in a compound, which may not reflect the actual number of atoms in complex molecules or network structures, as it does not show the exact number of atoms like the molecular formula does.
Step-by-step explanation:
The empirical formula may not represent the actual composition of a unit of a complex molecule or network structure. The empirical formula shows the simplest whole-number ratio of the atoms in a compound but does not indicate the actual number of atoms present. For instance, the molecular formula for glucose is C6H12O6, while its empirical formula is CH2O. To determine a compound's molecular formula from its empirical formula, additional information such as the molar mass is needed.
This is because many substances, especially larger or more complex ones, may have molecular formulas that are multiples of their empirical formulas. Furthermore, for ionic compounds, which do not form discrete molecular units like covalent compounds do, the formula mass is used instead of the molecular mass, and is based on the empirical formula.