Birth of the Atomic Theory

As a result of his work on relative weights, Dalton formulated the Law of Multiple Proportions, which states that when elements combine to form more than one compound, then the ratio of the masses of elements in the compounds are small whole number ratios of each other. For example, the elements carbon and oxygen form the two compounds carbon monoxide (CO) and carbon dioxide (CO ). The ratio of 

Relative Weights of Ultimate Gas Particles According to Dalton 

Hydrogen Azot (nitrogen) Carbon Oxygen Water 

Dalton s Law of Multiple Proportions meant that two elements combine in simple whole number ratios. Dalton believed that compounds found in nature would be simple combinations. Hence, knowing that hydrogen combines with oxygen to give water, Dalton s formula for water would consist of 1 H and 1 O. Its formula would be HO using modern nomenclature. Both Proust s Law of Definite Proportions and Dalton s Law of Multiple Proportions are outcomes of an atomic view of nature. In 1808 Dalton published his table of relative atomic weights along with his ideas on atomism in A New System of Chemical Philosophy. 

Because Dalton did not know the chemical formula for compounds, he assumed the greatest simplicity. This worked fine for some compounds such as CO or NO, but introduced error for other compounds, for example, assuming water was HO. Nevertheless, Dalton s ideas laid the foundation for the modern atomic theory. Dalton s ideas briefly summarized are  

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