Changes in Atomic Theory

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    Democritus

    Democritus
    Democritus was the man who came up with the idea of atoms. He thought that if you kept cutting something in half you would eventually get to a point where you wouldn't be able to cut it in half anymore. He did an experiment with an apple and discovered that his theory was true.
  • Isaac Newton

    Isaac Newton
    He proposed that atoms moved and caused things to move. This was the basis of his famous "Newton's Laws." He also wrote a book called "Opticks" about atoms and how they move.
  • John Dalton

    John Dalton
    He proposed the atomic theory stating that there are three distinct forms of atoms that are elastic fluids (gas), liquid, and solid.
  • Michael Faraday

    Michael Faraday
    He developed electrolysis and the laws of electrolysis, which is the process of splitting a molecule with electricity.
  • Dmitri Mendeleev

    Dmitri Mendeleev
    He created the first version of the periodic table by organizing the elements into 7 groups with similar properties. He also left spaces on the table for the undiscovered elements.
  • James Clerk Maxwell

    James Clerk Maxwell
    He proposed that electric and magnetic fields filled the void area in an atom.
  • G. J. Stoney

    G. J. Stoney
    He proposed that electricity was made of negatively charged particles. He called these particles electrons.
  • Willhelm Roentgen

    Willhelm Roentgen
    He used CRT rays to discover that the penetrating rays weren't affected by a magnetic field. He called these rays "x-rays."
  • Frederick Soddy

    Frederick Soddy
    He discovered isotopes in spontaneously decaying radioactive elements and calculated the discharge of energy put off through decay.
  • Hantaro Nagaoka

    Hantaro Nagaoka
    He proposed the Saturnian model for atomic structure. It showed an atom as flat rings of electrons orbiting a positively charged particle.
  • Albert Einstein

    Albert Einstein
    He proposed the famous equation of E=mc2.
  • Niels Bohr

    Niels Bohr
    He proposed the Bohr model for atomic structure. His model showed an atom as consecutive rings of electrons.
  • Paul Dirac

    Paul Dirac
    He proposed the idea of anti-particles. Anti-electrons were discovered in 1932 and anti-protons in 1955.
  • Period: to

    Glenn Seaborg

    He synthesized 6 new elements and suggested a change in the layout of the periodic table.
  • Enrico Fermi

    Enrico Fermi
    He created the first controlled chain reaction that released energy from an atom's nucleus.