atomic theory timeline

  • 380

    Democritus, 380 BC, Abdera, Greece

    Ideas & experiments:
    -Matter was composed of tiny particles called atoms.
    -They could join up with other atoms to create more atoms. Contribution to our understanding of the atom:
    -Brought up the idea that atoms exist. Sources:
    -http://www.timelineindex.com/content/view/1228
    -http://scienceworld.wolfram.com/biography/Democritus.html
  • Period: 380 to

    Discovery of the atom

  • Isaac Newtown,1704,Lincolnshire, England

    Ideas & experiments:
    -Proposed a mechanical universe with small solid masses in motion. Contribution to our understanding of atoms:
    -atoms are held together by attractions that we call forces. Sources:
    http://scienceworld.wolfram.com/biography/Newton.html http://scienceworld.wolfram.com/biography/Newton.html
  • John Dalton, 1803, Cumberland, England

    Ideas & experiments:
    1. All matter is composed of tiny particles called atoms.
    2. Atoms can’t be broken into smaller particles.
    3. Atoms of the same element are alike.
    4. Atoms join together in fixed ratios. Contributions to our understanding of the atom:
    -all matter is composed of tiny particles called atoms.
    - atoms of the same element are alike. Sources:
    http://www.brooklyn.cuny.edu/bc/ahp/FonF/Dalton.html
    -Heinemann Interactive Science 3
  • George Johnstone Stoney, 1894, Oak Park, Ireland

    Ideas & experiments:
    -Discovered electron- ‘atom of electricity’
    -the Stoney scale Contribution to our understanding of the atom:
    - discovered negative charge. Sources:
    http://atomictimeline.net/index.php
  • Joseph John Thomson, 1897, Manchester, England

    Ideas & experiments:
    -‘Plum pudding theory’
    -discovery of the electron and of isotopes Contributions to our understanding of atoms:
    -Atom is made up of a positively charged particle with tiny electrons scattered throughout the atom like raisins in a plum pudding. Sources:
    http://scienceworld.wolfram.com/biography/Thomson.html
  • Mark Planck, 1900, Germany

    Ideas & experiments:
    -used the idea of quanta (discrete units of energy) to explain hot glowing matter.
    -created Planck’s constant
    -created Planck’s Law of Black-body Radiation Contribution to our understanding of the atom:
    -Revolutionised our understanding of atomic and subatomic processes Sources:
    http://nobelprize.org/nobel_prizes/physics/laureates/1918/planck-bio.html
    http://scienceworld.wolfram.com/biography/Planck.html
  • Hanatora Nagaota, 1903, Omura, Japan

    Ideas & experiments:
    -‘Planetary model of atoms’- electrons revolving around the nucleus, bound by electrostatic forces. Contribution to our underdtanding of the atom:
    - Created a slightly incorrect model of an atom based on the solar system, whiched improved our understand of the stucture of atoms. Sources:
    http://en.wikipedia.org/wiki/Hantaro_Nagaoka
  • Robert Andrews Milikan, 1909, America

    Ideas & experiments:
    -‘Milliken oil drop experiment’- Successfully measured the charge of a single atom (1.60 x 10-19 coulombs) Contributions to our understanding of the atom:
    -allowed us to measure the charge to mass ratio of an electron. Sources:
    http://en.wikipedia.org/wiki/Robert_Andrews_Millikan
  • Ernest Rutherford, 1911, Britian & New Zealand

    Ideas & experiments:
    -Atom contained a dense nucleus containing all its positive charge. Contributions to our understanding of the atom:
    -Electrons could orbit a positively charged nucleus, like planets orbiting a sun. Sources:
    http://www.visionlearning.com/library/module_viewer.php?mid=50
  • Henry Gwyn-Jeffreys Moseley, 1914, England

    Ideas & experiments:
    -Each nucleus was characterised by an atomic number, equal to the number of unit positive charges associated with it.
    -Moseley Law that is an empirical law concerning the characteristic x-rays that are emitted by atoms Contributions to our understanding of the atom:
    -By rearranging the periodic table according to atomic number rather than atomic weight, a more systematic arrangement was obtained. Sources:
    http://atomictimeline.net/index.php http://www.infoplease.com/ce6/
  • Niels Bohr, 1922, Denmark

    Ideas & experiments:
    -‘Shell model’- Electrons could circle a nucleus without radiating energy only in orbits.
    -the liquid drop model of the atomic nucleus Contribution to our understanding of the atom:
    -developed an explanation of atomic structure that underlies regularities of the periodic table of elements. Sources:
    http://library.thinkquest.org/27948/bohr.html
    http://www2.lucidcafe.com/lucidcafe/library/95oct/nbohr.html
  • James Chadwick, 1932, England

    Ideas & experiments:
    -Discovered neutrons Contribution to our understanding of the atom:
    - Discovered negative charge in atoms. Sources:
    http://en.wikipedia.org/wiki/Atomic_theory
    http://www.visionlearning.com/library/module_viewer.php?mid=50
    http://atomictimeline.net/index.php