Atoms 1

Atomic Theory Timeline -1LJH

  • 340


    In 340 BC, Aristotle disagreed with Democritus theory of atoms. He believed that you would end up with a particle that could not be cut. Aristotle believed that matter is made of Earth, fire, air, and water.
  • 400

    Greek Philosopher Democritus

    Greek Philosopher Democritus
    400 BC

    Proposed that small particles called Atoms make up all matter.
  • John Dalton's Atomic Theory

    John Dalton's Atomic Theory
    He published his atomic theory. His theory states: All substances are made of atoms. They are small particles that cannot be created, divided, or destroyed. Atoms of the same element are exactly alike, & atoms of different elements are different. Atoms join with other atoms to make new substances.
  • John Dalton

    John Dalton
    Revised Atomic Theory
  • Dmitri Mendeleev

    Dmitri Mendeleev
    Developed the first periodic table of elements.
  • J.J. Thomson

    J.J. Thomson
    Identifies electrons as particles that are present in every atom. Plum-pudding Model.
  • Ernest Rutherford Gold-Foil Experiment

    Ernest Rutherford  Gold-Foil Experiment
    He discovery that most of an atom's mass is located in a dense region now called the nucleus.
  • Ernest Rutherford Revised J.J. Thomson's Model

    Ernest Rutherford Revised J.J. Thomson's Model
    This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space.
  • Niels Bohr

    Niels Bohr
    Bohr model of the atom
    This model shows that electrons are in energy levels.
  • Henry Moseley

    Henry Moseley
    He determined the number of protons in an atom. This is called the Atomic number.
  • Erwin Schrodinger, Werner Heisenberg, & other scientists

    Erwin Schrodinger, Werner Heisenberg, & other scientists
    They created the Electron Cloud Model.
  • James Chadwick

    James Chadwick
    He discovered the neutron, one of the particles in the nucleus of an atom.
  • Glenn Seaborg Modern Perodic Table

    Glenn Seaborg   Modern Perodic Table
    He devised the Modern Periodic Table.
  • Scientists in Switzerland

    Scientists in Switzerland
    They developed a scanning tunneling microscope, which is used to see atoms for the first time.