The distinction between a molecular formula and an empirical formula is fundamental in understanding chemical compounds. A molecular formula provides the actual number of each type of atom present in a molecule. For instance, glucose has the molecular formula C6H12O6, indicating it contains six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.
In contrast, the empirical formula represents the simplest whole-number ratio of the different types of atoms in a compound. For glucose, the empirical formula would be CH2O, which simplifies this ratio to the lowest whole numbers without representing the actual quantities of each atom.
This understanding highlights why the correct answer clearly identifies that the molecular formula shows the exact number of atoms, while the empirical formula conveys only the simplest ratio.