-
450
Democritus (460 B.C.)
Democritus developed the idea of atoms, but was dismissed by Aristotle, a well respected philosopher of that time. He had no evidence to back up his theory; he simply asked himself "If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further?" -
450
Aristotle (350 B.C.)
Aristotle did not believe in the atomic theory and thought all materials on Earth were made of four elements. He provided the method of gathering scientific facts such as gravity and levity. Gravity was the tendency for earth and water to sink, and levity the tendency for air and fire to rise. -
Dalton
Dalton discovered all atoms fo the elemnet are identical but are different from the atoms of thoer elements. He experimented with various chemicals that showed matter consiisting of lumpy particles (atoms). Dalton didn't know about their structure, but he knew that the evidence pointed to something fundamenta.. -
Thomson
Thomson discovered that atoms consist of a large sphere of uniform positve charge embedded with smaller negatively charged particles. He used "canal rays" which are different when gases were used and "cathode rays" were always identical regardless of the nature of the electrodes or gas used. His most famous model was called the "Plum Pudding" model. -
Rutherford
Rutherford determined that there is a large nucles with a positive charge. He then conducted the gold foil experiment, in which he shot alpha rays at gold foil indicating there was something there with a large positive charge. Bibliography
Harvey, Nicole. "Unit 5 Concept 2 - Atomic Theory." Unit 5 Concept 2 - Atomic Theory.pptx - Google Drive. N.p., n.d. Web. 27 Feb. 2014.
De Leon, Prof. N. "Rutherford Model of the Atom." Rutherford Model of the Atom. C101 Class Notes.inc, n.d. Web. 25 Feb. 2 -
Bohr
Bohr expanded on Rutherford's theory by stating protons are in the nucleus and neutrons surround them. He also said electrons only move in certain paths and the valence electron determines the chemical property of the element. Bohr applied the quantum theory to Rutherford's atomic structure by assuming that electrons travel in stationary orbits defined by their angular momentum. Bibliography
The-history-of-the-atom. N.p., n.d. Web. 27 Feb. 2014.
Walker, Jim. "History of Atoms." History of Atoms -
Heisenberg (1927) and Schrodinger (1926)
Heisenberg and Schrodinger shared a similar theory. They proved that no experiment can measure the position and momentum of a quantum particle simultaneously. Scientists call this the "Heisenberg uncertainty principle." Meaning that when someone is trying to figure out the exact position of a particle, uncertainty in the momentum gets larger. Which finally concludes that there is simply just a cloud surrounding the nucleus containing the approximate positions of the electrons within them. -
Heisenburg and Schrodinger
Bibliography
Walker, Jim. "History of Atoms." History of Atoms. N.p., Nov. 2004. Web. 26 Feb. 2014
G., Molly. "Timeline of the Atom." : Erwin Schrodinger. Watermark Template, Inc., n.d. Web. 27 Feb. 2014.
Harvey, Nicole. "Unit 5 Concept 2 - Atomic Theory." Unit 5 Concept 2 - Atomic Theory.pptx - Google Drive. N.p., n.d. Web. 27 Feb. 2014.
