Dalton's research was based on the works of several other scientists and chemists, such as Antoine Lavoisier's 1789 law of conservation of mass or law of definite proportions first proven by Joseph Louis Proust in 1799 (Atomic Theory).
However, Dalton's theory of atoms was not complete or entirely correct and his work was further improved by the works of Amadeo Avogadro and others. In 1897, J.J. Thompson revealed that the atom was not the smallest particle as he discovered the electron, proving that there are other particles called elementary particles. Thomposon was also the first to discover the existence of isotopes.
Atomic theory was further improved by the works of Ernest Rutherford, who "discovered that most of the mass and positive charge of an atom is concentrated in a very small fraction of its volume, which he assumed to be at the very center" (Atomic Theory), the center being called nucleos.
In 1913 Niels Bohr brought even more contribution to atomic theory as he elaborated the Bohr...
Louis de Broglie first presented the idea that electrons exhibit a degree of wave-like behaviour and Erwin Schrodinger further developed the idea. Werner Heisenberg discovered the principle of uncertainty based on the works of his predecesors.
Atomic theory, like any other scientifical theory, developed in time with the contributions of several valuable scientists which constantly improved the theories of their predecesors.
Bibliography
Ancient Atomism, first published Tue Aug 23, 2005; substantive revision Tue Oct 18, 2005, available at http://plato.stanford.edu/entries/atomism-ancient/#5;
Atomic Theory, available at http://en.wikipedia.org/wiki/Atomic_theory;
Carpi, Anthony, Atomic Theory I, the Early Days, available at http://www.visionlearning.com/library/module_viewer.php?mid=50;
History of atomic theory, available at http://encarta.msn.com/encyclopedia_761567432_9/Atom.html.
