Chemistry Timeline

By lremi19
  • 400 BCE

    Democritus

    According to Democritus' atomic theory, everything is made up of atoms. Democritus adopted the theory, developed it, and made a more detailed view of the theory https://www.reference.com/science/did-democritus-contribute-atomic-theory-4653045c78e24bd4

  • John Dalton

    He had came up with these 5 proofs about atomic theory 1.Elements are made of atoms
    2.Atoms cannot be created, destroyed or divided in chemical processes
    3.Atoms of the same element are the same
    4.Atoms of differing elements cannot be identical
    5.Atoms combine together in set ratios to form compound Not all are true, but for his time, this was a breakthrough in the atomic theory. http://www.answers.com/Q/Who_was_John_Dalton_and_what_did_he_do

  • Ernest Rutheford

    Rutherford’s atomic theory was that an atom had a central positive nucleus with negative electrons orbiting it. He developed this theory with his gold foil experiment. Ernest Rutherford’s gold foil experiment involved a round detecting screen with a slit in it and a slip of gold foil in the middle. The detecting screen had zinc sulfide in it to allow him to detect the particles after they went through the foil.
    https://www.reference.com/science/ernest-rutherford-s-atomic-theory-4e543e2f9d598a51

  • J.J Thomson

    Discovered electrons by using a cathode ray tube. He demonstrated that cathode rays were negatively charged. With that, he also had studied electrons in neon. http://www.abcte.org/files/previews/chemistry/s1_p5.html

  • Eugen Goldstein

    He had discovered the proton. After discovering anode rays, he also had worked with many different gases, especially hydrogen. https://www.reference.com/science/did-eugen-goldstein-discover-1f4e0cbc5705099b

  • Robert A. Millikan

    Robert Millikan's contribution to atomic theory came as a result of his oil-drop experiment, which measured an electron's charge. He also did some work with the mass of the electron and size of the electrons charge https://www.reference.com/science/millikan-s-contribution-atomic-theory-7a42f09a420fed89

  • James Chadwick

    He had discovered the neutron. Neutrons help stabilize the protons in the atom's nucleus. Because the nucleus is so tightly packed together, the positively charged protons would tend to repel each other. Neutrons help to reduce the pulling between protons and stabilize the atom's nucleus. Neutrons always stay in the nucleus of atoms and they are about the same size as protons. However, neutrons do not have any electrical charge.