List the defects in Mendeleev periodic table.

Following are the defects in the Mendeleev periodic table:

  1. Anomalous Pairs

    The following pairs of elements don’t follow the follow Mendeleev’s Principles:

    Cobalt (58.9) with a higher atomic mass precedes Nickel (58.6) in the periodic table.

    Tellurium (127.6) with a higher atomic mass than Iodine (126.9) precedes it in the periodic table.

  2. Grouping of chemically dissimilar elements

    Elements such as Copper and Silver bear no resemblance with the alkali metals, but they have been placed together in the first group.

  3. Position of Isotopes

    According to Mendeleev’s Periodic Law, isotopes of an element must be given separate places in the periodic table because they have different atomic masses.

  4. Electronic arrangement

    It does not explain the electronic arrangement of elements.

  5. Separation of chemically similar elements

    Elements that are chemically similar such as Gold and Platinum have been placed in separate groups.

  6. The position of hydrogen

    Hydrogen was not given a fixed position because it was considered in Group IA as well as in Group VIIA.

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