Timeline of the Atom

  • 322


    He believed in the four elements of air, earth, water and fire.  Aristotle felt you would always have a smaller piece of matter if you keep cutting it in half.
  • 400


    He had a theory that stated that matter could not be devided into smaller pieces. They would eventually become the smalles they can become and invisible. He named the smallest pieces "atomos" which mean "not to be cut."
  • Jan 13, 1144

    Second Crusade

    Second Crusade
    The Second Crusade is started by Bernard of Clairveaux after the Christian kingdom of Edessa falls to Muslims.
  • Jan 13, 1149

    Oxford University

    Oxford University
    Oxford University is founded in England.
  • Jan 13, 1348

    Black Plague

    Black Plague
    The Black Plague in Europe kills about 75 million people.
  • Jan 13, 1517

    Martin Luther

    Martin Luther
    Martin Luther
    An Augustinian monk, Martin Luther, nails his 95 theses to the church door in Wittenberg. He unknowingly initiated the Protestant revolution.
  • Jamestown

    The English settle in Jamestown.
  • Treaty of Paris

    Treaty of Paris
    The French and Indian War is ended with the Treaty of Paris. Britain gains all of North American east of the Mississippi, important parts of India, and various islands from the French. Many American colonists, most notably George Washington, gain military experience in the conflict.
  • Antonie Lavosier

    Antonie Lavosier
    He proposed the Combustion Theory which was based on sound mass measurements. He named oxygen.  He also proposed the Law of Conversation of Mass which represents the beginning of modern chemistry.
  • Joseph Proust

    Joseph Proust
    He proposed the Law of Constant Composition.
  • John Dalton

    John Dalton
    John DaltonDalton's theory stated that the atoms of different elements could be distinguisehd by differences in their weights.
  • Amadeo Avagadro

    Amadeo Avagadro
    His hypothesis says that at the same temperature and pressure, equal volumes of gases contain the same number of molecules or atoms.
  • Origin of Species

    Origin of Species
    Charles Darwin publishes Origin of Species.
  • William Crookes

    William Crookes
    He studied the effects of sending an electric current through a gas in a sealed tube. The tube had electrodes at either end and a flow of electrically charged particles moved from one of electrodes. This electrode was called the cathode, and the particles were known as cathode rays .
  • Henri Becquerel

    Henri Becquerel
    While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very penetrating rays.
  • J.J. Thomson

    J.J. Thomson
    Discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, he estimated the value of the charge itself.
  • Madame Curie

    Madame Curie
    CurieStudied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium.
  • Max Planck

    Max Planck
    He used the idea of quanta, (discrete unit of energy) to explain hot glowing matter
  • Robert Millikan

    Robert Millikan
    Determined the unit charge of the electron with his oil drop experiment at the University of Chicago. This allowed the calculation of the mass of the electron and the positively charged atoms. 
  • Albert Einstein

    Albert Einstein
    He published the famous equation E=mc^2
  • Earnest Rutherford

    Earnest Rutherford
    Established that the nucleus was very dense, very small and positively charged. He also assumed that electrons were located outside outside the nucleus.
  • Henry Moseley

    Henry Moseley
    Using x-ray tubes, he determined the charges on the nuclei of most atoms. He wrote "The atomic number of an element is equal to the number of protons in the nucleus". This work was used to reorganize the periodic table based upon atomic number instead of atomic mass.
  • Niels Bohr

    Niels Bohr
    Developed an explanation of  atomic structure that underlies regularities  of the periodic table of elements. His atomic model had atoms built up of successive orbital shells of electrons.
  • Louis deBroglie

    Louis deBroglie
    His theory states that particles can behave like waves, and waves (radiation) can behave like particles.
  • Heisenberg

    He described  atoms a formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminacy - you can not know both the position and velocity of a particle.
  • Erwin Schrodinger

    Erwin Schrodinger
    Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom.
  • James Chadwick

    James Chadwick
    Using alpha particles he discovered a neutral atomic particle with a mass close to a proton. Because of this the neutron was discoverd.
  • World War II

    World War II
    Germany invaded Poland and started World War II.
  • Neil Armstrong

    Neil Armstrong
    Neil ArmstrongNeil Armstrong, an American, steps out of his lunar landing module to become the first human being to set foot on the moon.
  • Nelson Mandela

    Nelson Mandela
    Future South African President walks out of jail after 27 years in the custody of the white apartheid government.