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Differentiate between the arrangement of elements in Mendeleev's periodic table and the modern periodic table.

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Mendeleev’s Periodic Table

Modern Periodic Table

  • Mendeleev's periodic table is based on atomic mass. Elements are arranged in increasing order of their atomic masses.
  • Modern periodic table is based on atomic number. Elements are arranged in increasing order of their atomic numbers.
  • There are no separate positions for isotopes of an element as their atomic masses are different.
  • Separate positions are not required as they have same atomic numbers.
  • Some elements of higher atomic masses have been placed before elements of lower atomic masses.
  • No such problems occur in this table. All elements are in proper order.
  • Some dissimilar elements are grouped together while some similar elements are not grouped together.
  • All similar elements are grouped together.
  • Electronic configuration of an element cannot be calculated from its position.
  • Electronic configuration of an element can be easily calculated from its position.
  • Mendeleev's periodic table contains about 66 elements.
  • Modern periodic table contains about 112 elements.

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