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John Dalton FRS (/ ˈ d ɔː l t ən /; 5 or 6 September 1766 – 27 July 1844) was an English chemist, physicist and meteorologist. [1] He introduced the atomic theory into chemistry.
In 1804, Dalton explained his atomic theory to his friend and fellow chemist Thomas Thomson, who published an explanation of Dalton's theory in his book A System of Chemistry in 1807. According to Thomson, Dalton's idea first occurred to him when experimenting with "olefiant gas" and "carburetted hydrogen gas" .
Modern atomic theory is not based on these old concepts. [2] [3] In the early 19th century, the scientist John Dalton noticed that chemical substances seemed to combine with each other by discrete and consistent units of weight, and he decided to use the word atom to refer to these units. [4]
John Dalton's union of atoms combined in ratios (1808) Similar to these views, in 1803 John Dalton took the atomic weight of hydrogen, the lightest element, as unity, and determined, for example, that the ratio for nitrous anhydride was 2 to 3 which gives the formula N 2 O 3. Dalton incorrectly imagined that atoms "hooked" together to form ...
The law of definite proportions contributed to the atomic theory that John Dalton promoted beginning in 1805, which explained matter as consisting of discrete atoms, that there was one type of atom for each element, and that the compounds were made of combinations of different types of atoms in fixed proportions. [5]
John Dalton's list of atomic weights and symbols. The law of definite proportions was formulated by Joseph Proust around 1800 [5] and states that all samples of a chemical compound will have the same elemental composition by mass.
Dalton's atomic symbols, from his own books. Scientists had recently discovered that when elements combine to form compounds, they always do so in the same proportions, by weight. John Dalton thought that for this to happen, each element had to be made of its own unique building blocks, which he called atoms.
Dalton's idea also differed from the idea of corpuscular theory of matter, which believed that all atoms were the same, and had been a supported theory since the 17th century. [19] To help support his idea, Dalton worked on defining the relative weights of atoms in chemicals in his work New System of Chemical Philosophy, published in 1808. [19]