History of Atom

By Sammy Mahnke
  • 460 BCE

    Democritus

    Democritus
    First to believe that everything in the universe was made up of atoms, which were microscopic and indestructible.

  • John Dalton

    John Dalton
    Developed the atomic theory. He had 4 parts to it. 1) All matter is made of atoms. Atoms are indivisible and indestructible.
    2) All atoms of a given element are identical in mass and properties.
    3) Compounds are formed by a combination of two or more different kinds of atoms.
    4) A chemical reaction is a rearrangement of atoms.

  • Dmitri Mendeleev

    Dmitri Mendeleev
    Took the elements and put them into the periodic table.

  • Eugene Goldstein

    Eugene Goldstein
    He discovered protons with the experiments he did with cathode rays which would knock electrons of atoms and attract them to a positively charged electrode.

  • J.J. Thomson

    J.J. Thomson
    Discovered the electron.

  • Max Planck

    Max Planck
    Developed quantum theory. Planck made the assumption that energy was made of individual units, or quanta. Developed the law that describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T.

  • Robert Millikan

    Robert Millikan
    Began a series of experiments to determine the electric charge carried by a single electron. He got his results from his oil-drop experiment in which he replaced water with oil.

  • Ernest Rutherford

    Ernest Rutherford
    He was the first to discover that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons, which became known as the Rutherford model (or planetary model) of the atom.

  • Niels Bohr

    Niels Bohr
    Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element.

  • Erwin Schrodinger

    Erwin Schrodinger
    He took the Bohr atom model one step further. Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom.

  • James Chadwick

    James Chadwick
    Discovered Neutrons in Atoms.

  • Werner Heisenberg

    Werner Heisenberg
    He developed new theories in quantum mechanics about the behavior of electrons which agreed with the results of previous experiments. Heisenberg is most famous for his "uncertainty principle", which explains the impossibility of knowing exactly where something is and how fast it is moving.