Atomic Model Scientists Timeline

By Hjones71
  • 600 BCE

    Thales of Miletus

    Thales of Miletus
    Thales took a piece of amber and rubbed it with fur. When the piece of amber attracted bits of hair feathers, and other light objects, Thales suggested that it carried a mysterious force. However, he did not quite connect the force with the atomic particle.
    Link text
    Link text
  • Period: 600 BCE to

    Years

  • 460 BCE

    Democritus

    Democritus
    Democritus asked himself this question: "If you break a particle of matter in half, and the break it in half again, how many breaks will you have to make before you can break it no further?" Therefore he believed all matter was composed of tiny, invisible, and indestructible units. He called these units "atoms".
    Link text
    Link text
  • 332 BCE

    Aristotle

    Aristotle
    Aristotle dismissed Democritus's atomic idea as worthless. Instead, he believed that all matter was the same, but behaved differently according to qualities present. He also believed in four elements as well as the theory that regardless of how many times you cut matter in half, it would become smaller.
    Link text
    Link text

  • Antoine Lavoisier

    Antoine Lavoisier
    Lavoisier discovered the role oxygen plays in combustion. He named oxygen in 1778 and hydrogen in 1783.
    Link text
    Link text

  • John Dalton

    John Dalton
    His atomic theory still remains valid in modern chemistry.
    1. All matter is made of atoms.
    2. Atoms are indivisible and indestructible.
    3. Compounds are formed by a combination of two or more different kinds of atoms.
    4. A chemical reaction is a rearrangement of atoms.
    He also assumend that water contains one atom of hydrogen and one atom of oxygen.
    Link text
    Link text

  • Michael Faraday

    Michael Faraday
    Faraday coined words such as Electrode, Cathode, and Ion. He also discovered Electromagnetic Induction, which is the principal behind the electric transformer and generator.
    Link text
    Link text

  • Dmitri Mendeleev

    Dmitri Mendeleev
    Mendeleev published the periodic table. It was the first classification of the periodic table, in which he arranged them in order of atomic mass.
    Link text
    Link text

  • J.J. Thomson

    J.J. Thomson
    Thomson performed a series of experiments in 1897 that were designed to study the nature of Electric Charge in a high-vacuum cathode-ray tube. After his experiment, Thomson suggested that the model of the atom was a sphere of positive matter in which electrons are positioned by electrostatic forces.
    Plum Pudding Model:
    1. Atom is composed of Electrons
    2. Plum: Negatively Charged
    3. Pudding: Positive Charged
    Link text

  • Max Planck

    Max Planck
    Developed Planck's Constant: 6.62607004 x 10^-34 m^2 kg/s
    After developing his constant, he had to revert one of his most cherished beliefs, that the second law of thermodynamics was an absolute law of nature.
    Link text
    Link text

  • Robert A. Millikan

    Robert A. Millikan
    One of Millikan's first major successes was the accurate determination of the charge carried by an electron using the "Falling-Drop Method." This discovery led to the atomic structure of electricity. He would later verify Einstein's, photoelectric equation.
    Link text
    Link text

  • Ernest Rutherford

    Ernest Rutherford
    Rutherford described the atom as a tiny, dense, positively charged core called a "Nucleus." Rutherford also found that light, negative constituents called electrons, circulate at some distance. (Like that of Planets) Rutherford conducted an experiment known as the "Gold Foil Experiment", which marked the discovery that the atom was composed of mostly empty space, with a positive charged nucleus. (Unstable Atoms)
    Link text

  • Niels Bohr

    Niels Bohr
    In 1913, Bohr developed and published his version of the atomic structure, which is now known as the Bohr Model. His model depicts the atom as a small, positively-charged nucleus that is surrounded by negatively-charged electrons that travel in a circular orbit around the nucleus.
    Link text
    Link text

  • Erwin Schrödinger

    Erwin Schrödinger
    Known for Schrödinger Equation, which is the science of submicroscopic phenomena known as Quantum Mechanics. Schrödinger described the form of the probability waves that govern the motion of small particles, and how the waves are altered by external influences.
    Link text
    Link text

  • James Chadwick

    James Chadwick
    In 1932, James Chadwick bombarded Beryllium atoms with alpha particles, causing unknown radiation to be produced. After his experiment, Chadwick interpreted the radiation as being composed of particles with a neutral electric charge, and the approximate mass of a proton. His discovery eventually became known as the "Neutron."
    Link text
    Link text