How did John Dalton's theory explain the difference between carbon monoxide and carbon dioxide?

John Dalton’s atomic theory explained the difference between carbon monoxide and carbon dioxide through his law of multiple proportions. This law states that when two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other exist in a ratio of small whole numbers.12

Dalton observed that carbon and oxygen can combine to form two distinct compounds. Based on his atomic theory, he proposed that these compounds were formed by combining atomic building blocks of different masses in definite proportions. Specifically, he recognized that carbon dioxide contains twice as much oxygen by weight as carbon monoxide, resulting in a simple integer ratio of 2:1 for the oxygen content between the two compounds.13

While Dalton’s foundational argument regarding atomic combinations was correct, his specific formulas were often based on his "rule of greatest simplicity," which assumed the simplest possible atomic combination for a compound. Overcoming the limitations of his initial assumptions regarding molecular formulas required later developments, such as Amedeo Avogadro's hypothesis.314