A molecule of acetone and a molecule of propyl aldehyde are both made from 3 carbon atoms, 6 hydrogen atoms, and 1 oxygen atom. The molecules differ in their arrangement of atoms. How do formulas for the two compounds compare? Both compounds have unique molecular formulas and structural formulas.

Both compounds have the same structural formula, but have unique molecular formulas.

Both compounds have the same molecular formula, but have unique structural formulas.