Beginning of Essay
John Dalton developed the first useful atomic theory of matter around 1803. In the course of his studies on meteorology, Dalton concluded that evaporated water exists in air as an independent gas. Solid bodies can't occupy the same space at the same time, but wate ....

Middle of Essay
.... reactions. He was the first to associate the ancient idea of atoms with stoichiometry. The existence of atoms was first suggested more that 2000 years before Dalton's birth. (Newton's speculations about atoms in the Principia were carefully copied by hand into Dalton's notebooks.) Atoms of an element cannot be created, destroyed, broken into smaller parts or transformed into atoms of another element. Dalton based this hypothesis on the law of conservation of mass and on centuries of experimental evidence. Some of the details of Dalton's original atomic theory are now known to be incorrect. But the core concepts of the theory (that chemical reacti ....