Here's why:

* Chemical names provide information about the structure and functional groups of a molecule. They are based on a system of nomenclature that helps us understand the composition of the compound.

* Chemical formulas represent the exact number and types of atoms in a molecule. For example, H₂O is the chemical formula for water, indicating two hydrogen atoms and one oxygen atom.

Example:

* Chemical name: Ethanol

* Chemical formula: C₂H₅OH

The name "ethanol" tells us it is an alcohol with an ethyl group. However, the formula C₂H₅OH gives us the exact number and types of atoms (2 carbon, 6 hydrogen, and 1 oxygen).

Therefore, a chemical name describes the structure and functional groups, but a chemical formula precisely defines the composition.