Atomic Theory

  • 384

    Aristotle

    Aristotle
    Theorized that all matter is made from the elements wind, fire, water, and earth.
  • 460

    Democritus

    Democritus
    Called the particle ‘atomos’. Theorized that we are all made of particles.
  • 500

    Alchemists

    Alchemists developed a theory that all metal is made up of sulfur and mercury and they believed that any metal could be turned into gold. They spent many years trying to find someone who could turn another metal into gold.
  • Benjamin Franklin

    Benjamin Franklin
    KIte experiment led to the discovery that mater has charges.
  • Antoine Lavoisier

    Antoine Lavoisier
    Classified an element as a simple substance.
  • Charles Augustine de Coulumb

    Charles Augustine de Coulumb
    Discovered that like forces repel.
  • Michael Faraday

    Michael Faraday
    Michael Faraday was able to complete a number of experiments using static, batteries, and animal electricity in order to produce electrostatic attraction, electrolysis, and magnetism. He thought that only one electricity existed and differing current and voltage would produce different types of results.
  • Dmitri Mendelev

    Dmitri Mendelev
    Dmitri Mendeleev had just published the book Principles of Chemistry. He had also published the periodic table with all the known elements and predicted a few in order to complete the table.
  • Wiliam Crookes

    William Crookes identified the first known sample of Helium.
  • Henri Becquerel

    Henri Becquerel
    Dsicovered radiation by studying X-rays and studying fluoresence.
  • J. J. Thompson

    J. J. Thompson
    Joseph John Thomson continued to investigate and experiment with cathode rays. Through his work he was able to discover the existence of electrons and isotopes. He also came up with his own model of the atom known as the plum pudding model. He thought that an atom was a sea of electrons suspended in positively charged particles.
  • Ernest Rutherford

    Ernest Rutherford
    Ernest Rutherford coined the terms alpha ray and beta ray as a way to distinguish the different types of radiation.
  • Max Planck

    Max Planck
    Max Planck presented what is now known as the Planck postulate which states that energy can only be a multiple of an elementary unit of energy. E=hv(nu). h is Planck’s constant and v(nu) is the frequency of the radiation.
  • John Dalton

    John Dalton
    Created concept of ‘mole’.
  • William Crookes

    William Crookes
    William Crookes started to research and experiment with radioactivity. He was able to discover Uranium-X or protactinium.
  • Pierre and Marie Curie

    Pierre and Marie Curie
    : Pierre and Marie Curie were awarded with the Noble Prize, along with Henry Becquerl, for the joint discovery of radioactivity, a term coined by Madame Curie. Pierre and Marie were also able to discovered polonium and radium. They now have a unit of radioactivity named after them called a “curie” (3.7 x 10^10 decays per second).
  • Albert Einstein

    Albert Einstein
    Albert Einstein published a paper that explained the photoelectric effect which he was later given a Nobel Prize for. The photoelectric effect states that electrons are emitted from substances in any state when they absorb energy from light.
  • Robert Milikan and Harvey Flecther

    Robert Milikan and Harvey Flecther
    Robert Milikan and Harvey Flecther did the oil drop experiment and were able to calculate the charge of a single electron. Harvey Flecther’s work on this experiment was kept secret until after his own death.
  • Ernest Rutherford

    Ernest Rutherford
    Ernest Rutherford completed the gold foil experiment where he discovered the existence of a nucleus and created a new model of the atom, disproving Thomson’s plum pudding model. In the experiment alpha particles were beamed through a very thin sheet of gold foil. Many alpha particles were beamed back which proved that there was a nucleus. His model is also known as the planetary model of the atom.
  • Niels Bohr

    Niels Bohr
    Explained the spectrum of atomic hydrogen using Rutherford’s research.
  • Werner Heisenberg

    Werner Heisenberg
    Created matrix mechanics, the predecessor of quantam mechanics.
  • Erwin Schrödinger

    Erwin Schrödinger
    Erwin Scrodinger published a paper in January on wave mechanics and what is now known as the Schrodinger equation. This paper, and the ones that succeeded it, are celebrated for creating a revolution in quantum mechanics and in physics and chemistry.
  • Werner Heisenberg

    Werner Heisenberg
    His most important contribution is the Heisenberg Uncertainty Priciple. We can know neither the velocity or location of an electron at any given time.
  • Werner Heisenberg

    Werner Heisenberg
    Published book , 'The Physical Principles of Quantum Theory' explaining his ideas.
  • Louis Debroglie

    Louis Debroglie
    Discovered that electrons can act like both waves and particles.
  • James Chadwick

    James Chadwick
    Used Curie's research to discover neutron. Discovered neatrons and protons ahve similar mass. Now concluded that nucleus contain neutrons and protons.