Explain the comparison of mendeleev and modern periodic table


Mendeleev’s periodic table is, based on the relation of elements’ properties as dependent on the atomic weight of the element. But the Modern periodic table considers atomic number as the fundamental property that decides the properties of elements.

The modern periodic table does correct the defects of Mendeleev’s periodic table. For example, in Mendeleev’s periodic table, in the element pairs, Argon-potassium, cobalt-nickel, tellurium-iodine and thorium and protactinium, elements with higher atomic mass precede the element with lower atomic weight. However, it is the right places for them but is against Mendeleev’s periodic law.

These elements atomic number shows the reverse order compared to atomic mass. The supposed to be wrong positions in Mendeleev’s table has the right explanation justifying their positions.

Uneven grouping of elements:

In Mendeleev’s periodic table, coinage metals of copper, silver, and gold are, grouped with very active alkali metals. Manganese metal was grouped with halogens in the seventh group. The defects are rectified in the Modern periodic table.

Position of isotopes:

Isotopes with higher atomic weights could not be accommodated in Mendeleev’s table. As isotopes have the same atomic number as the stale atom, they do not need any separate location in the modern periodic table.

  • No reasons were offered for the triad elements of the viii group. No such special grouping is given in the modern table.
  • Mendeleev’s periodic table was for the arrangement of sixty-three elements known at that time.
  • The modern table accommodates all the 118- natural and synthetic elements.

The atomic number is much fundamental property distinguishing each element and hence a better basic nature to decide the physical and chemical properties of elemental atoms than atomic weights.

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