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History of the Atom

History of the Atom. Democritus hypothesized that atoms were undestructable . He also thought they were indivisable . His theories were not based on scientific method . Democritus 460 B.C . http://www.wikigallery.org/wiki/painting_318696/Charles-Antoine-Coypel/The-Cheerful-Democritus.

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History of the Atom

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  1. History of theAtom

  2. Democritushypothesizedthatatomswereundestructable. He alsothoughttheywereindivisable. Histheorieswerenotbasedonscientificmethod. Democritus 460 B.C. http://www.wikigallery.org/wiki/painting_318696/Charles-Antoine-Coypel/The-Cheerful-Democritus

  3. Dalton used experimental observationsto come up with a 4-part scientifictheory. Thefirstpart is thatallelements are composed of tiny individual particlescalled “atoms”. Part 2 is thatatoms of thesameelement are identical. The atoms of any one element are different from those of any other element.Part 3 is atoms of differentelements can chemically combine in wholenumber ratios. Part 4 is that chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction. Dalton 1803 http://www.1902encyclopedia.com/C/CHE/chemistry-014.html

  4. Mendeleev formulated a periodic table similar to the one we use today. Elements were grouped according to recurring trends in their properties. Mendeleev 1869 http://www.bluffton.edu/~bergerd/nsc_111/science2.html http://chemistry.about.com/od/famouschemists/p/mendeleevbio.htm

  5. Goldstein concluded that cathode-ray tubes with a perforated cathode emit a glow from the end of the tube near the cathode. Goldstein concluded that in addition to the electrons there is another ray that travels in the opposite direction, from the anode toward the cathode. Eugene Goldstein 1885 http://chemed.chem.purdue.edu/genchem/history/goldstein.html http://www.dipity.com/montelt292/History-of-Atomic-Theory/

  6. Becquerel was a French physicist who discovered radioactivity through his investigations of uranium and other substances. In 1903 he shared the Nobel Prize for Physics with Pierre and Marie Curie. Henri Becquerel 1896 http://www.nndb.com/people/608/000072392/ http://www.britannica.com/EBchecked/topic/58020/Henri-Becquerel

  7. ThomsomplayedwithCathoderaytubeexperimentsjustlikeGoldstein. He measuredchargetomass ratio of negativelychargedparticlesfordifferent gases. He alsocreatedthe “raisian in thedough” model of theatom. J.J. Thomson 1897 http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/atomic-and-nuclear-structure/thomson.aspx

  8. Rutherfold’sgoldfoilexperimentdisprovedThomson’satomicmodel. He showedthattheatom is mostlyjustemptyspace. Most of themass is contained in a compact, has a positivelycharged center and a nucleus. Ernest Rutherford 1907 http://en.wikipedia.org/wiki/Ernest_Rutherford

  9. Millikanexperimentallydeterminedthatthechargewascarriedbytheelectron. He usedmass/ charge ratio createdby Thomson. He usedthisforcalculatingthemass of anelectron. Millikan 1910 http://www.xtimeline.com/evt/view.aspx?id=71291

  10. Soddy proposed that the same elements exist in different forms, with nuclei having the same number of protons but different numbers of neutrons. His theory of isotopes explained that different elements can be chemically indistinguishable but have different atomic weights and characteristics. Frederick Soddy 1913 http://theanatomyofmelancholy.tumblr.com/post/1054790261/radiochemist-frederick-soddy-born-september-2 http://www.nndb.com/people/286/000099986/

  11. Bohr was the first to apply the quantum concept. The concept restricted the energy of a system to certain discrete values, to the problem of atomic and molecular structure. For this work, he received the Nobel Prize for Physics in 1922. Neils Bohr 1913 http://www.nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-bio.html http://www.britannica.com/EBchecked/topic/71670/Niels-Bohr

  12. Heisenberg was a German physicist and philosopher who discovered a way to formulate quantum mechanics in terms of matrices. For this discovery, he was awarded the Nobel Prize for Physics for 1932. Heisenberg 1925 http://en.wikipedia.org/wiki/Werner_Heisenberg http://www.britannica.com/EBchecked/topic/259761/Werner-Heisenberg

  13. Chadwick discovered the neutron in 1932. His discovery formed the base for the investigation of the tougher questions of nuclear physics: the nature of the nucleus and its forces. In 1935, he received the Nobel Prize for Physics. Chadwick 1932 http://www.light-science.com/chadwick.html http://scientistsinformation.blogspot.com/2011/03/sir-james-chadwick-1891-1974.html

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