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450
Democritus(c 400 b.c)
Democritus is credited to be the first person to discover the atom. His model was quite symbol(just a round ball that contained protons, neutrons, and electrons) as he only dicovered the existence of atoms and not the substructure of the atom. Most of his works have been lost over time so it is not exactly possible to discover what reaserch he used, but none the less he introduced the idea of the atom which has been expanded over the last two thousand years. "Democritus." The-History-of-the-Atom -
450
Aristotle(c 330 b.c)
Aristotle studied many feilds of science which he later used to be become a philosepher and spread his teachings. Aristotle however did not believe in atomic theory and taught that matter was made off elements not atoms. Even though this was later disproved his teaching were taught for over two thousand years. His theory lated until the mid 1800's when this was disproven by Jhon Dalton. "Aristotle." The-History-of-the-Atom -. N.p., n.d. Web. 27 Feb. 2014. -
John Dalton
Dalton's atomic theory was that all matter is made up of very small particles known as atoms. He did not discover the structure of atoms. While Dalton was living, there was no way to explain the difference between atoms and molecules. He also created a way to classify elements based on weight.
http://www.britannica.com/EBchecked/topic/150287/John-Dalton/217770/Atomic-theory -
J.J. Tompson
Tompson is credited for creating the plum pudding model which consist of an overall positive "pudding" with negativly charged "plums" embedded within. J.J. Tompson used expirements with cathode rays to discover that positive rays were different when different gases were used while negative rays are identical no matter the nature of the gas.
"A Brief History of Modern Atomic Theory." Chemistry Tutorial : History of Atomic Theory. N.p., n.d. Web. 25 Feb. 2014. -
Earnest Rutherford
Rutherford discovered that atoms consist of a tiny nucleus that contains positive particles called protonsand most of t and a large space surrounding the atom that contains negative particles called electrons. His expirements were comprised of gold foil and positivly charged alpha particles that were shot at the foil where most went right through, suggesting the particles were mostly empty space, but some did bounce back which must mean there is a tiny, positive nucleus attached. -
Rutherford citation
"A Brief History of Modern Atomic Theory." Chemistry Tutorial : History of Atomic Theory. N.p., n.d. Web. 25 Feb. 2014. -
Bohr
Bohr found that atoms consist of a positively charged nucleas that is orbited by negativly charged electrons that orbit the nucleas with set paths, and the outer most electrons determined the chemical properties. He also stated that the electrons can drop from a higher energy level to a lower one, releasing energy in the process.
Crepeau, Bob. "Niels Bohr." Niels Bohr (2006): 1. Science Reference Center. Web. 27 Feb. 2014. -
Heisenberg and Schrodinger
Schrodinger is credited to propose that wlectron were waves instead of particles. Heisenberg had the idea that the electons were still particles.While the two had opposing theories, they were both mathmatically the same. Their version of the atomic model didn't have energy levels and instead had a "cloud".
Walker, Jim. "History of Atoms." History of Atoms. N.p., Nov. 2004. Web. 26 Feb. 2014. http://www.nobeliefs.com/atom.htm.
