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Mendeleev's Periodic Law


Dmitri Mendeleev's periodic law states that if the elements are arranged in order of increasing atomic weight the properties would repeat in a orderly fashion.  He developed this idea when he constructed an eight-column table of the elements.  In his periodic table, blank spaces had to be left in order to group elements with similar properties in the same column.  Mendeleev proposed that these blank spaces represented unknown elements.  Using the systematic way properties changed from element to element, Mendeleev predicted the properties of the unknown elements.


  • Examine the modified periodic table (Groups I, II, III, IV, V, VI,
and VII).  It contains elements and their properties.  It also contains
blank spaces for unidentified elements.

  • Examine the list of unknown elements and their properties.

  • Using the periodic trends of the selected properties, identify
and record the unknown elements in their proper blank spaces on
the modified periodic table.

  • You may refer to the periodic table on pages 144-145


Abbreviations:  ionization energy -- IE, atomic radius -- AR, and
melting point -- MP.