Question

defects in the mandeleev periodic table​

Answer 1

1. positive hydrogen: in Mendeleev periodic table hydrogen is placed in group first A all through it shows similarity in properties with the element of group 1 A as well as with the elements of group 7 A that's why in this periodic table the position of hydrogen is not clear or controversial. 2. inversion in the periodic table: in order to satisfy the periodic law in this table certain pairs of element it had to be we placed in the reverse order of atomic weights example Cobalt (atomic weight 58.9) has been placed before nickel (atomic weight 58.7). 3. position of isotopes:as we know isotopes are the atoms of same elements having same atomic number but different atomic masses thus separate places should be e given to these elements in the periodic table but mandeleev periodic table had no place for these elements. 4. grouping of dissimilar elements together and similar elements separately certain dissimilar elements example cu Ag Au which have no no resemblance with alkali metals. 5. case of periodicity: mendeleev also failed to explain the case of periodicity of elements. 6. position of lanthanoids: in this table 14 elements after lathanum called lanthanoids have been placed together with lanthanum at a single place despite of the fact that it there atomic masses are different similar is true for the 14 elements after actinium called the the actinoids because all of the above defects the scientist tried from time to time to modify this table

Answer 2

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