Periodic table

Development of the periodic table

  • Dobereiner

    Dobereiner proposed the law of triads. He found the alkali metal triad and the halogen triad. The alkali metal triad consisted of Sodium, lithium and potassium. The halogen triad consisted of chlorine, bromine and iodine. He suggested that naturally occuring elements came in threes, the middle element when the triad is ordered in atomic mass is the mean average of the 2 either side of it.
  • 62 elements

    By 1860, 62 elements had been discovered.
  • John Newlands

    John Newlands
    John Newlands improved on Dobereiners law of the triads, by creating the rule of octaves. He put all the known elements into order of relative atomic mass, and after doing this noticed that every 8 elements appeared an element that is similar to the one 8 before or after that.
  • Dmitri Mendleev

    Dmitri Mendleev
    Dmitri Mendeleev arranged the periodic table in the way that we are used to today. He produced the way they're ordered as he noticed that elements of similar atomic mass have also got similar properties. The gaps in the periodic table were where he actually predicted some elements would be discovered.
  • Moseley

    Moseley essentially polished off after mendeleevs work. He arranged the elements by atomic number, as apposed to the atomic mass that Mendeleev used.