Atomic Theory Timeline

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    Democritus

    Democritus
    He thought when you kept cutting an object in half, eventually you would end up with an atom that is inseperable. He also thought atoms were made of single materials formed into different shapes and sizes. The theory of Democritus and Leucippus held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; that between atoms lies empty space; that atoms are indestructible; have always been, and always will be, in motion; that there are an infinite number

  • Dalton

    Dalton
    Dalton published the Atomic Theory in 1803. He said that all substances are made of atoms and that atoms couldn't be created, divided, or destroyed.

  • Thomson's Cathode- Ray Tube

    Thomson's Cathode- Ray Tube
    Thomoson said that there are particles inside an atom. He discovered that electrons were in atoms. Thomson, in 1897, was the first to suggest that the fundamental unit was over 1000 times smaller than an atom, suggesting the subatomic particles now known as electrons. Thomson discovered this through his explorations on the properties of cathode rays.

  • Rutherford's Gold Foil Experiment: "Shooting Gallery"

    Rutherford's Gold Foil Experiment: "Shooting Gallery"
    Rutherford studied the parts of an atom and determined that some went through the gold foil and some did not. drogen was known to be the lightest element, and its nuclei presumably the lightest nuclei. Now, because of all these considerations, Rutherford decided that a hydrogen nucleus was possibly a fundamental building block of all nuclei, and also possibly a new fundamental particle as well, since nothing was known from the nucleus that was lighter.

  • Bohr's Electron Levels

    Bohr's Electron Levels
    Bohr proposed that electrons move around the nucleus in a certain path. He also helped predict the atomic behavior. The Bohr model of the atom, the theory that electrons travel in discrete orbits around the atom's nucleus.he shell model of the atom, where the chemical properties of an element are determined by the electrons in the outermost orbit.

  • Chadwick's Neutron Experiment

    Chadwick's Neutron Experiment
    Chadwick discovered the neutron and he also confirmed the existence of the atom. He also made it possible to create elements heavier than uranium in a lab.