Atomic Theory Timeline

By snam21
  • 500 BCE


    Is the art of understanding, deconstructing, and reconstruction of matter. It is composed of the four basic elements. (fire, earth, water, and air)
  • 400 BCE


    Everything is composed of 'atoms', which are physically but not geometrically indivisible.
  • 400 BCE


    Disagreed with Democritus.
    Everything is a combination of the four elements: earth, fire, water, and air.
    Theory that a mass of incomprehensible size was everywhere: he called this 'hyle' (there was no separate particles for each material, it was all one.)
  • 400 BCE


    Theory of atom-ism. The world is composed of an infinite number of solid, indestructible, indivisible atoms that interact with one another. What separates the atoms is the void, which is empty space.
  • 1500

    George Bauer

    George Bauer
    Presented the first scientific classification of minerals (based on their physical properties) and described many new minerals: their occurrence and mutual relationship.
  • 1540


    Paracelsus Theory: combination of Aristotelian Theory of Matter, alchemical correspondences, chemical therapy in medicine
  • Robert Boyle

    Robert Boyle
    Wrote a book that overturned Aristotle's conception of the four elements, and replaced it with the modern idea of an element, namely that an element is a substance that cannot be separated into simpler components by chemical methods.
  • Isaac Newton

    Isaac Newton
    Theorized a mechanical universe with small solid masses in motion.
  • Jons Jakob Berzelius

    Jons Jakob Berzelius
    Accepted John Dalton's atomic theory and made a new system of chemical symbols.
  • LaVoisier

    Law of Conservation of Mass: matter cannot be created or destroyed, only rearranged.
    Discovered that water is made of Hydrogen and Oxygen.
  • Proust

    Law of Definite Proportions: A pure substance will always contain the same elements, combined in the same proportion by mass.
  • Gay-Lussac

    Law of Combining Volumes: At a constant temperature and pressure, volumes of reacting gases and gaseous products are in the ratio of small numbers.
  • John Dalton

    John Dalton
    Law of multiple proportions: same two elements can combine in different compound; ratio of first element is fixed, while the second element varies.
    Proposed first atomic theory, all matter is made up of tiny indivisible atoms, atoms of the same element are the same, atoms of different elements are different, atoms combine in while number ratios to form compounds.
  • Amedeo Avogadro

    Amedeo Avogadro
    Avogardo's hypothesis: equal volumes of gases under the same conditions that have the same number of particles.
  • Dmitri Mendeleev

    Dmitri Mendeleev
    Formulated the table of elements listing them by their atomic weight and grouping them into families with similar characteristics, 'periodic law'.
  • Wilhelm Roentgen

    Wilhelm Roentgen
    Discovered x-rays.
  • Henri Bequerel

    Henri Bequerel
    Discovered that uranium ores emit radiation, resembling x rays because it exposed film.
  • J. J. Thomson

    J. J. Thomson
    Used cathode rays to discover the electron, measured the bending of the rays to determine the charge to mass ratio of the electron.
    Modified the cathode ray tubes to soon discover the positively charged proton.
  • Max Planck

    Max Planck
    Quantum theory; energy is not emitted constantly, but in small plackets called quantum.
  • Albert Einstein

    Albert Einstein
    Photoelectric effect; when light of a certain frequency shines on a metal, electrons are emitted.
  • Robert Millikan

    Robert Millikan
    Performed the oil drop experiment which determined the charge of electrons as negative.
  • Ernest Rutherford

    Ernest Rutherford
    Studied substances, especially alpha particles. Conducted the gold foil experiment; he bombarded gold foil with alpha particles, most particles passed through the foil, but some were deflected. He concluded that the atom is mostly empty space, but also discovered the very small nucleus core.
  • Niels Bohr

    Niels Bohr
    Improved upon the atomic model by trying to answer the question;
    Why aren't electrons pulled into the nucleus?
    Electrons travel in definite energy levels without radiating energy
    Electrons in each orbit have a certain amount of energy
    Energy increases as the distance from nucleus increases.
    Energy loses energy by dropping energy levels.
  • Henry Mosely

    Henry Mosely
    Used x ray experiments to discover the atomic number of an element.
  • Arthur Compton

    Arthur Compton
    Discovery of the Compton effect, which demonstrated the particle nature of electromagnetic radiation
  • Louis de Broglie

    Louis de Broglie
    Debroglie's hypothesis; if waves can behave like particles, then particles can behave like waves.
  • Erwin Shrodinger

    Erwin Shrodinger
    Schrodinger's wave equation:
    Treat the electron like a wave
    Developed an equation used to determine the probability of finding the electron in any given place around the nucleus.
    Solutions to the equation are quantum numbers.
  • Werner Heisenberg

    Werner Heisenberg
    Heisenberg's uncertainty principle: it's impossible to know both position and velocity of an electron at the same time.
  • James Chadwick

    James Chadwick
    Discovered the neutron.
  • Murray Gell-Mann

    Murray Gell-Mann
    Description and classification of subatomic particles.
  • Carlo Rubbin

    Carlo Rubbin
    Discovery of W and V particles.
  • Peter Higgs

    Peter Higgs
    Higgs Boson, a subatomic particle; the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles