History of the Atom Timeline by Katie Hostetler and Melissa Dardenne

By katie.hostetler2017
  • 450

    Democritus (430 BC)

    Democritus (430 BC)
    Discorved the atom approximately 430 BC.
    He believed that all matter is made up of tiny particles called atoms, which he declared to be the smallest element of matter. He did not conduct any expiriements and only came up with this theory by asking the question "if you were to break a peice of matter in half several times until you have none left?" His model of the atom was a round sphere with no protons, neutrons, or electrons.
  • 450

    Aristotle (340 BC)

    Aristotle (340 BC)
    Aristotle - history of the atom
    Made his conclusion about the atomic theory approximately 340 BC. He did not agree with Democritus' theory of the atom and believed that all matter was made up of the four elements: fire, water, earth, and air. More people agreed with Aristotle and discared Democritus' theory for almost 2000 years, since Aristotle was Alexander the Great's mentor.

  • Dalton

    Dalton
    John Dalton believed that all matter is made of atoms, that atoms all have different characteristics that make them unique, and that there are three different types of atoms that exist. The simple atoms are what make elements, the compound atoms are simple molecules, and complex atoms are complex molecules. He conducted an expiriment, discovering only certain gases could be combined in certain amounts, even if they contain the same elements. His model was the same as Democritus'; a round sphere.

  • Thomson

    Thomson
    Discovered the electron and added it to the pravious atomic model, which now contained (+) and (-) charges, but the nucleus had still not been discovered yet (he did not discover the proton). He expirimented with cathode rays, which were made by currents of electricity inside glass ubes. He speculated the rays were made of particles that were smaller and were actaully inside of the atom, which were the electrons. His model of the atom is a sphere that contains (+) and (-) particles.

  • Rutherford

    Rutherford
    Discovered the nucleus of the atom. Conducted an expiriment where he shot a ray of alpha particles at a sheet of gold foil. The particles bounced off of the foil in different directions, and he concluded that they were hitting something with a larger mass: the nucleus, which he said made up most of the mass a (+) charge in the atom. His model of the atom was a (+) charged center (nucleus) with negativley charged electrons surrounding it.

  • Bohr

    Bohr
    Proposed that atoms had different layers of energy feilds, and the outer feilds could cotain more electrons than the inner feilds. Came up with the quantum theory which states that electrons can be in wave form or particle form. His model of the atom is the most commonly used today, and consists of a nucleus containing protons and nutrons and the elctrons surrounding the nucleus ni the energy feilds.

  • Heisenberg & Schrodinger

    Heisenberg & Schrodinger
    Both scientists came up with the quantum mechnics theory which proved that you cannot measure the exact position and momentum of a quantum particle at the same time. The electrons are moving so fast that you cannot determine an exact position, so they are contained in an electron cloud. The Heisenburg uncertianty pricipal states that if you are trying to detremine the exact position of a particle, the uncertianty of the momentum increases. Their model is a nucleus with an electron could.

  • BIBLIOGRAPHY (3)

    Palermo, Elizabeth. "Niels Bohr: Biography & Atomic Theory." LiveScience. TechMedia Network, 14 May 2013. Web. 26 Feb. 2014. http://www.livescience.com/32016-niels-bohr-atomic-theory.html.
    Pfeifer, Erin. "Niels Bohr." Niels Bohr. N.p., 2000. Web. 25 Feb. 2014. http://wwwp.cord.edu/faculty/ulnessd/legacy/fall2000/pfeifer/nielsbohr.htm.
    Weisstein, Eric W. "Dalton, John (1766-1844)." Dalton, John (1766-1844) -- from Eric Weisstein's World of Scientific Biography. WOLFRAM Research, 2007. Web. 26

  • BIBLIOGRAPHY (4)

    "Erwin Schrodinger/ Werner Heisenberg - The Atom." Erwin Schrodinger/ Werner Heisenberg - The Atom. Google Sites, n.d. Web. 27 Feb. 2014.
    "Atom History." Atom History. N.p., n.d. Web. 27 Feb. 2014.
    "Joseph John Thomson." Homepage of the Chemical Heritage Foundation. Chemical Heritage Foundation, n.d. Web. 25 Feb. 2014.
    "Models of the Atom." EVERYTHING SCIENCE. N.p., n.d. Web. 25 Feb. 2014.

  • BIBLIOGRAPHY (2)

    Harvey, Nicole. "Atoms and the Periodic Table Unit 5 Concept 2." Unit 5 Concept 2. ZHS, Zachary. 26 Feb. 2014. Reading.
    Inc., McGraw-Hill. "Cathode Ray Tube." Cathode Ray Tube. McGraw-Hill, n.d. Web. 26 Feb. 2014. http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::100%25::100%25::/sites/dl/free/0072512644/117354/01_Cathode_Ray_Tube.swf::Cathode+Ray+Tube.

  • BIBLIOGRAPHY

    "The Bohr Model." The Bohr Model. University of Tennessee, n.d. Web. 26 Feb. 2014. http://csep10.phys.utk.edu/astr162/lect/light/bohr.html.
    "Dalton Atomic Theory." Dalton Atomic Theory. Chemsoc Timeline, 2013. Web. 26 Feb. 2014. http://www.rsc.org/chemsoc/timeline/pages/1803.html.
    "Ernest Rutherford." Homepage of the Chemical Heritage Foundation. Chemical Heritage Foundation, n.d. Web. 26 Feb. 2014. <http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/atomic-and