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Drawbacks of mendeleve\'s preodic law |
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Answer» Drawbacks/Demerits of Mendeleev\'s periodic table :-1) Hydrogen\'s positionHydrogen resembled the properties of both alkali metals(like lithium) and also that of halogens(like iodine). Hence, the position of hydrogen(whether hydrogen is to be placed with halogens or alkali metals) was not specified.2) Position for IsotopesIsotopes are those with same atomic no: and different mass no:s.Mendeleev\'s\xa0periodic table was based on arranging elements in increasing order of atomic masses. But isotopes were not included in his periodic table.3) Certain elements were arranged in reverse order. Elements having higher atomic mass were placed in front(or before) the elements with less atomic mass. Example - Cobalt and NickelCobalt being more heavier than Nickel ,was placed before Nickel , in the Mendeleev\'s periodic table. He could not assigned correct position of hydrogen.Isotopes were discovered long time after his table.The atomic masses could not increase in regular manner |
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