Atomic Theory

  • 300


    He believed that the earth consisted of four major elements; earth, fire, air, and water. Aristotle disagreed with Democritus and thought his ideas were worthless. Aristotle believed that reasoning was a better source of information than experimentation.
  • 400


    He was the first to theorize about the atom. He believed it was the smallest piece of matter. He used to word “atomos” which means indivisible.
  • Alchemists

    Alchemists were philosophers that created theories abou matter overtime. There is no specific experiment. Alchemists are also called hermits.
  • Benjamin Franklin

    Benjamin Franklin
    He believed that there is an electric fluid present in all bodies and energy is gained or lost when objects are rubbed against each other. He stated that objects with opposite charges attract and same charges repel.
  • Antoine Lavoisier

    Antoine Lavoisier
    He established The Law of Conservation of Mass. This stated that energy cannot be created or destroyed.
  • Jeremias Richter

    Jeremias Richter
    He proved the law of definite proportions by weighing compounds and discovering that the ratio of elements were always the same.
  • Joseph Proust

    He analyzed sources of different compounds and found that the ratio was always the same of elements in a compound. This became the law of definite proportions.
  • John Dalton

    John Dalton
    He established the modern atomic theory.
  • MIchael Faraday

    MIchael Faraday
    His discoveries led to the idea that atoms had an electrical component. He used electrodes and water in his experiment to discover that electrical forces joined atoms into compounds.
  • William Whewell

    William Whewell
    He created the terms cation, anion, cathode, and anode by the negative and positive charges.
  • Julius Plucker

    Julius Plucker
    He saw that when gas was put into a cathode ray one end of the gas lights up. By putting a magnet near the light, the light moved.
  • Dmitri Mendeleev

    Dmitri Mendeleev
    He created the periodic table of elements by organizing the elements by atomic weights.
  • William Crookes

    William Crookes
    He studied the effects of cathode rays. He aided in the discovery that atoms were made up of a lot of empty space.
  • Wilhelm Roentgen

    Wilhelm Roentgen
    He used cathode rays to discover fluorescent rays, now called x-rays
  • Henri Becquerel

    Henri Becquerel
    He studied fluorescent properties of uranium salts. He contributed to the discovery of radioactivity.
  • Marie and Peirre Curie

    Marie and Peirre Curie
    They worked with Bequerel to discover spontaneous radiation. They later won the nobel prize in physics in 1903.
  • JJ Thomson

    JJ Thomson
    He discovered the electron by using cathode rays. He established the plum pudding model.
  • Wilhelm Wein

    Wilhelm Wein
    He proved that canal rays deflected off of magnetic and electric fields proving cathodes are negative and anodes are positive.
  • Max Planck

    Max Planck
    He believed atoms can emit quanta. His work was used by Einstein.
  • H.G.J. Moseley

    H.G.J. Moseley
    He proved van den Broek’s observation by studying the frequencies of x-rays in cathode rays. He discovered that the frequencies depended on the metal used in the anode which proved protons existed.
  • Albert Einstein

    Albert Einstein
    He proved that light was quantized because light is made of photons. He proved that photons are proportional to frequency.
  • Robert Millikan

    He performed the oil drop experiment with Thomson. He measured the charge of an electron
  • Ernest Rutherford

    Ernest Rutherford
    He performed the gold foil experiment. He established that the atom has a nucleus and the rest is empty space. He also predicted the existence o
  • Niels Bohr

    Niels Bohr
    He updated Rutherford's version of the atom to show the directions of electrons. He also proved the orbits of electrons and how electrons could jump levels of orbit.
  • Van den Broek

    Van den Broek
    He suggested that it was a mistake to compare the atomic weight of an atom with the charge of the nucleus. He proved that the estimate of a charge on the nucleus is equal to the atomic number of the element.
  • Louis-Victor de Broglie

    Louis-Victor de Broglie
    He created an equation that showed that energy is proportional to mass and speed when moving through space. He also stated that wave length is inversely proportional to momentum.
  • Werner Heisenburg

    Werner Heisenburg
    He established quantum mechanics. He was also the creator of the uncertaintly principle and calculated the behavior of electrons.
  • Erwin Schrodinger

    Erwin Schrodinger
    He calculated how to find the location of an electron using Bohrs model. His new model introduced the new concept of subenergy levels.
  • CJ Davisson

    CJ Davisson
    He tested de Broglie’s prediction that electrons could have the properties of particles and waves. He confirmed this theory by defracting electrons in an experiment.
  • James Chadwick

    James Chadwick
    He discovered an unknown radiation with the approximate max of a proton. His discovery led to the addition of the neutron to the atomic model.
  • Binning and H. Rohrer

    Binning and H. Rohrer
    They created scanning tunneling microscopy. This is used to see individual atoms within a metal.
  • Eugen Goldstein

    Eugen Goldstein
    He proved that cathode rays glowed on the side of the cathode showing that the other side anode was positively charged. The protons and electrons move through tiny holes on the anode side that he called canal rays.