How does a molecular formula differ from an empirical formula?

The correct answer highlights that a molecular formula represents the actual number of atoms of each element present in a molecule of a compound. This formula provides detailed information about the composition of a substance, indicating precisely how many of each type of atom are present. For example, the molecular formula for glucose is C6H12O6, which reveals that each molecule consists of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.

In contrast, an empirical formula shows the simplest whole-number ratio of the elements in a compound without detailing the actual number of atoms. For glucose, the empirical formula would be CH2O, indicating that the ratio of carbon to hydrogen to oxygen atoms is 1:2:1, but not giving any indication of how many total atoms are in the glucose molecule itself.

The options that do not pertain to the distinction between these two types of formulas focus on different aspects, such as combining elements or identifying gas volumes, which are not directly related to molecular versus empirical formulas.