At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
In nearly 17th century, Robert Boyle did experiments with gases and stated that gases are made up of small tiny particles. He was the first who said the atomic nature of substance. 1: In 1774, Antoine Lavoisier stated that oxygen is the key substance involved in all combination reaction. Before that Priestley prepared oxygen by heating mercuric oxide. 2: Lavoisier in his experiments proved that during combustion reaction, there is no change in mass of substance. 4:So he stated that during chemical reaction the mass of substance is neither created or destroyed which is popularly known as Law of conservation of mass. 5:Although the law of conservation of mass is not valid in case of nuclear reactions where a fraction of mass is converted to energy, it is applicable for all normal chemical reactions. 6:In the following year Proust stated that in a pure compound the constituent elements are always present in a fixed ratio. This is called as Law of definite proportions. 7:For example in ammonia (NH3), the atoms nitrogen and hydrogen are always present in 14:3 ratio. 8:After this law, Law of multiple proportions was also stated which states that the mass of second element combining with fixed mass of first element will be in simple ratio. 9:For example in carbon monoxide and carbon dioxide (CO and CO2), the mass of oxygen combining with 12g of carbon is 16g and 32g respectively. 10:Hence they are in the ratio of 1:2. These laws underline the need for an atomic theory which can accompany the established facts. Reference: http://goo.gl/STbMHq