Which statement describes the molecular formula?

Which statement describes the molecular formula?

• A. The simplest ratio of atoms
• B. The actual number of atoms of each element in a compound
• C. The total charge of the compound
• D. The lattice arrangement of ions

Answer: (B)

The molecular formula represents the exact number of atoms of each element in one molecule. It tells you the real counts, not just a simple ratio. For example, water has two hydrogen atoms and one oxygen atom in each molecule, so the molecular formula is H2O. This is different from the empirical formula, which shows only the simplest whole-number ratio of atoms in a compound; some substances share the same empirical and molecular formulas (like water), while others have an empirical formula that’s a smaller multiple of the actual molecule (for instance, glucose has empirical formula CH2O but molecular formula C6H12O6). Ionic compounds aren’t described by discrete molecules but by formula units in a lattice, so the concept of a molecular formula doesn’t apply in the same way there. The molecular formula does not specify the charge or how ions are arranged in a solid. So the molecular formula is the actual number of atoms of each element in a molecule.

The molecular formula represents the exact number of atoms of each element in one molecule. It tells you the real counts, not just a simple ratio. For example, water has two hydrogen atoms and one oxygen atom in each molecule, so the molecular formula is H2O. This is different from the empirical formula, which shows only the simplest whole-number ratio of atoms in a compound; some substances share the same empirical and molecular formulas (like water), while others have an empirical formula that’s a smaller multiple of the actual molecule (for instance, glucose has empirical formula CH2O but molecular formula C6H12O6). Ionic compounds aren’t described by discrete molecules but by formula units in a lattice, so the concept of a molecular formula doesn’t apply in the same way there. The molecular formula does not specify the charge or how ions are arranged in a solid. So the molecular formula is the actual number of atoms of each element in a molecule.