Development of the Periodic Table

By hammelj
  • Period: to

    johann Dobereiner

  • Law Of Triads

    Middle element in the triad had atomic weight that was the average of the other two members
  • Period: to

    Dimitri Mendeleev

    proposed ordering the elements on atomic wheight & propoties
  • Period: to

    John Newlands

  • The first Periodic Table

    The list was constructed as a helical graph wrapped around a cylinder--elements with similar properties occupied positions on the same vertical line of cylinder
  • law of octaves

    In Incrasing atomic mass every 8 elements the propoties repeat
  • Lothar Meyer develops an early version of the periodic table, with 28 elements organized by valence

  • Mendeleev's periodic table

    In 1871 Mendeleev revised the 17-group table with eight columns (the eighth group consisted of transition elements). This table exhibited similarities not only in small units such as the triads, but showed similarities in an entire network of vertical, horizontal, and diagonal relationships. The table contained gaps but Mendeleev predicted the discovery of new elements.
  • noble Gasses

    in 1895 the first of the noble gases was discovoured (argon ,Ar)
  • Moseley's Periodic Law

    Soon after Rutherford's landmark experiment of discovering the proton in 1911, Henry Moseley (1887-1915) subjected known elements to x-rays. He was able to derive the relationship between x-ray frequency and number of protons. When Moseley arranged the elements according to increasing atomic numbers and not atomic masses, some of the inconsistencies associated with Mendeleev's table were eliminated. The modern periodic table is based on Moseley's Periodic Law (atomic numbers).