An empirical formula represents the simplest whole number ratio of atoms in a compound, whereas a molecular formula indicates the actual number of atoms of each element present in a molecule.

For instance, glucose has the empirical formula $CH_2O$, which reflects the ratio of carbon, hydrogen, and oxygen atoms as $1:2:1$. In contrast, the molecular formula of glucose is $C_6H_{12}O_6$, indicating that each molecule contains six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.

Another example is ethene, which has the empirical formula $CH_2$, corresponding to one carbon atom and two hydrogen atoms. However, the molecular formula for ethene is $C_2H_4$, signifying that each molecule comprises two carbon atoms and four hydrogen atoms.

Both empirical and molecular formulas are crucial for understanding the composition and properties of compounds. Additionally, they are instrumental in calculating the molar mass of a compound, which plays a vital role in stoichiometric calculations.

In summary, the empirical formula provides the simplest whole number ratio of atoms within a compound, while the molecular formula reveals the actual number of each type of atom in a molecule. A solid grasp of these formulas is essential in chemistry, as they are foundational for determining the composition and characteristics of various compounds.