Atomic theory

History of Atomic Theory

  • 400


    In 400 BC, Democritus became the first peron to claim that all matter was made up of tiny atoms that are indistructible and indivisible.This set up investigation to what makes up matter for the following melleniums. (Sorry I couldn't make it go to BC years)
  • 410


    Aristotle taught that matter was not made up of atoms, but made up of pieces of four substances: earth, water, fire, and air. This theory made Democritus' theory be overlooked for years but was finally disproven as Atomic Theory grew.
  • USA

    America becomes an independent country
  • Joseph Proust

    Joseph Proust
    Established the Law of Definite Proportions, which states that in a compound the number of atoms are consistently proportional to one another. For example, if there are 2 hydrogen atoms to 4 oxygen atoms, then there are 4 hydrogen atoms to 8 oxygen atoms.
  • John Dalton

    John Dalton
    Dalton claimed that all matter was made up of atoms, and atoms of a given element have similar masses. He also said chemical reactions are the rearrangements of atoms, and that compounds are the combination of atoms of 2 different elements.
  • Civil War Starts

    Civil War Starts
    Confederate troops attack Fort Sumter, starting the Civil War.
  • First Car is invented

    First Car is invented
    Gottlieb Daimler invents the first prototype of the modern gasoline engine used in cars. Karl Benz uses this to create the first practical automoble.
  • Henri Becquerel

    Henri Becquerel
    Becquerel discovered that objects can emit light through phospherence. His discovery at the time would be explained years later when the discovery of photons being absorbed into atoms would emit light.
  • J.J. Thomson

    J.J. Thomson
    J. J. Thomson discovers that there are tiny electrons that make up the outer parts of an atom and affect its behavior.
  • Max Planck

    Max Planck
    Planck formulates the Quantum Theory: E=Nhf. This equation allowed physicists to explain that energy is released through quanta, not through wavelengths. He also created Planck's constant: 6.63 X 10^-34 joules per second. This opened doors for new theories and eventually Einstein's Theory of Relativity.
  • Albert Einstein

    Albert Einstein
    In 1905, Einstein proved mathematically the existence of atoms in matter. This was among the earliest theories about atoms and set up much more investigation for the century to come.
  • Robert Millikan

    Robert Millikan
    Millikan's Oil Drop experiment helps him discover the unit charge of electrons, which allows for the calculation of the mass of electrons and positively charged atoms.
  • Ernest Rutherford

    Ernest Rutherford
    Rutherford tested Thomson's Plum Pudding model, and through this discovered that most of an atom's mass must be centered in the nucleus. This not only disproved Thomson's theory, but set up the idea that electrons orbit around a nucleus like planets around a sun. Although this theory has been disproven and modified, the model is still the mostly used model today to show what we believe an atom looks like
  • World War I Starts

    World War I Starts
    Gavrilo Princip assassinates Franz Ferdinand, which acts as a catalyst for WWI.
  • Women get right to vote

    Women get right to vote
    The amendment that gave women the right to vote is ratified.
  • Niels Bohr

    Niels Bohr
    Bohr was the first scientist to discover that electrons circlearound the nucleus of an atom at different energy levels.
  • Erwin Schrodinger

    Erwin Schrodinger
    Schrodinger created the Quantam Mechanical Model, which took the Bohr Model a step farther by using mathematical equations to predict the location of an electron as part of an atom. This model introduced the ideo of sub-energy levels.
  • Louis de Broglie

    Louis de Broglie
    This theory states that electrons act like both particles and waves. His ideas were the basis for the Wave Mechanics Theory which explains how an atom produces and emits energy.
  • James Chadwick

    James Chadwick
    James Chadwick discovers the existence of the Neutron, and wins the Nobel Prize for his discovery.
  • Elvis Presley is Born

    Elvis Presley is Born
    He was just a Hound-dog, cryin' all the time (because he was a baby and they cry a lot).
  • Werner Heisenberg

    Werner Heisenberg
    Heisenberg created matrix mechanics, which was the first of many future versions of quantam mechanics.
  • Jackie Robinson

    Jackie Robinson
    Jackie Robinson becomes the first African-American Major League Baseball Player.
  • The Beatles are formed

    The Beatles are formed
    Paul McCartney, John Lennon, Ringo Starr and George Harrison decide on the band name "The Beatles" for their little rock group in Liverpool, England.