Atomic Theory Timeline

  • 460


    Democritus's work was done around the time of 460-457 BC. He tried to prove that everything was made up of atoms. His inspiration was Leucippus, the founder of atomism. He proposed The Atomic Theory, and had work on many other topics.
    (Please look at my note cards for sources for my information)
  • Period: 460 to

    Dates of Reasearch

  • John Dalton

    John Dalton
    John Dalton's work was done between 1766 and 1844. He was trying to define the atom as it was by Democritus, whom he was influenced by. These are the four ideas of Dalton's Atomic Theory:
    1) All matter is made of atoms. Atoms are indestructible and indivisible.
    2) All atoms of a given element are identical in mass and properties.
    3) Compounds are formed by a combination of two or more atoms of a different kind.
    4) A chemical reaction is a rearrangement of atoms
  • JJ Thomson

    JJ Thomson
    JJ Thomson's work was done between the years of 1856 and 1940, he questioned if there was any more to the atom. He was influenced by James Clerk Maxwell, and Wilhelm Rontgen. JJ Thomson discovered electrons, in order to do this he measured the speeds and charges of particles. He concluded that the particles (electrons) are 2000 times smaller. He thought electrons had a positive charge, and orbited very rapidly. He was also knighted in 1908.
  • Dmitri Mendeleev

    Dmitri Mendeleev
    Dmitri Mendeleev's work was done in the 1860s, he was trying to classify elements based upon their chemical properties, he was influenced by John Dalton. Dmitri Mendeleev also helped to develop the periodic table, and was considered to be the 'father' of the periodic table
  • Max Planck

    Max Planck
    Max Planck's work was done around 1864, he was asking how the intensity of electromagnetic radiation emitted by a black body depends on the frequency, and the temperature of the body. Max was influenced by Albert Einstein, Otto Hahn, and Lise Meitner. In his experiment he created maximum light from minimal electricity, and showed how much energy is emitted at different frequencies for a certain temperature of a black body. With this experiment he proposed The Planck Black-body Radiation Law.
  • Ernest Rutherford

    Ernest Rutherford
    Ernest Rutherford was influnenced by Alexander Bickerton, his teacher, he was trying to discover if X-rays could have an effect on gases. He observed the nuclear nature of atoms, and radioactive decay. In the experiment that was conducted (the Geiger-Marsden experiment) alpha particles were aimed at a peice of gold foil, a screen was placed behind the foil. The screen was looked at with a microscope to see if any alpha particles had passed through the gold foil. (Continued)
  • Ernest Rutherford (Continued)

    Ernest Rutherford (Continued)
    He also theorized the existence of neutrons in his model of the atom.
  • Erwin Schrodinger

    Erwin Schrodinger
    Erwin Schrodinger's work was done between 1906 and 1955 he wondered how atoms orbit from a geometric point of view. He was influenced by Max Planck, Albert Einstein, Niels Bohr, and Arnold Sommerfeld. He developed Quantum Mechanics (and helped develop wave mechanics). In his model of the atom he had the orbits of electrons, th whole atom looked more like a sphere. Erwin Schrodinger also came up with the Schrodinger Cat Paradox.
  • Robert Millkan

    Robert Millkan
    Robert Millkan was influenced by Albert Einstein, he was trying to figure out what the charge of a single electron was. In order to do that his experiment included him finding the mass, and measuring the terminal velocity of an oil drop. With that information her was able to find the density, and calculate the charge of the drop.
  • Niels Bohr

    Niels Bohr
    Neils Bohr's work was done between the years of 1911 and 19133, he was questioning the structure of the atom. Neils was influenced by Ernest Rutherford and Max Planck, and his father, who was a physicist. He came up with the 'planetary model' of the atom with orbiting electrons.
  • James Chadwick

    James Chadwick
    James Chadwick questioned weither there was more to an atom than just protons and electrons, and discovered the neutron. He was inspired by Ernest Rutherford, and John Cockroft. He also helped with the Manhattan Project during WW2.
  • Werner Heisenberg

    Werner Heisenberg
    Werner Heisenberg's work was done between 1924 and the 1970s, he was exploring the concept of nuclear fission, his work influenced by Otto Hahn and Fritz Strassman. He proposed the Principle of Uncertainty, and described the subatomic particlle plasma.
  • Murray Gell-Mann

    Murray Gell-Mann
    Murray Gell-Mann's work was done between 1958 and the 1980s, he was trying to discover if protons neutrons and electrons were made up of other particles. He was inspired by Richard Feynmman. Murray Gell-Mann proposed the concept of Quantum Chromodynamics, he also played a role in keeping the string theory alive in the 70s and 80s.