"[Democritus:] Everything was composed of atoms, which moved randomly in a vacuum, in a void. They collided into each other by chance. This was the absolute negation of Aristotle's idea that everything had a purpose as divinely ordained [the theory of the Four Elements]."Dr. Hugh SalzburgChemistry HistorianThe idea that matter is composed of atoms goes back to the Greek philosophers, notably Democritus, and has never since been entirely lost sight of, though there have been periods when alternative views were more generally preferred. Newton's contemporaries, Robert Hooke and Robert Boyle, in particular, were atomists, but their interpretation of the sensation of heat as random motion of atoms was overshadowed for more than a century by the conception of heat as a subtle fluid dubbed caloric. It is a tribute to the strength of caloric theory that it enabled the French scientist Sadi Carnot to arrive at his great discoveries in thermodynamics. In the end, however, ...view middle of the document...
In recent years the recognition that certain localized disturbances in a fluid, the so-called solitary waves, might persist for a very long time has led to attempts, so far unsuccessful, to use them as models of fundamental particles. Rudjer Boscovich based his theory on Newtonian mechanics and published it in 1758 within his Theoria philosophiae naturalis redacta ad unicam legem virium in natura existentium. According to Boscovich, atoms are stuctureless points, which exhibit repelling and attracting forces on each other, depending on distance. John Dalton used the atomic theory to explain why gases always combine in simple ratios. It was with Amedeo Avogadro's work, in the 19th century, that scientists began to distinguish atoms and molecules. In modern times atoms have been observed experimentally.A BRIEF HISTORY OF ATOMIC THEORY DEVELOPMENTYear Milestone Scientist(s)~400 BC The first coherent atomic theoryDemocritus1804 First "modern" atomic theoryJ. Dalton1869 First periodic tableD. Mendeleev1896-9 Radioactivity discovered and identifiedH. Becquerel, M. Curie, E. Rutherford1897 Electron discoveredJ.J. Thomson1909-11 Identification of an atomic nucleusE. Rutherford, H. Geiger1913 Mass of electron determinedR. Millikan1913 Positive charge in the nucleus and naturally occuring isotopes discoveredJ.J. Thomson1913 Atomic number determined, periodic table reorganizedH. Moseley1919 Proton existance confirmed, neutron proposedE. Rutherford1931 Neutron IdentifiedJ. Chadwick---- Summary and Symbology---------I did not receive any help for this, other than the sources listed, and I did not allow anyone to copy me._________________________________Oct. 16th, 2004 Sources:http://www.learner.org/channel/workshops/chemistry/workshop1/1_5.htmlhttp://zebu.uoregon.edu/~js/glossary/atomic_theory.htmlhttp://en.wikipedia.org/wiki/Atomic_theoryhttp://acpcommunity.acp.edu/Facultystaff/genchem/GC1/lecture/assign/atomic/hisatom.htmhttp://zebu.uoregon.edu/~js/21st_century_science/images/atoms_history.gif
