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Chaitan Singh
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Asked: 2020-10-21T04:39:38+00:00 In:

How could the Modern Periodic Table remove various anomalies of Mendeléev’s Periodic Table?

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NCERT Solution for Class 10 Science Chapter 5
Periodic Classification of Elements
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Intext Questions
Page No-90
Questions No-1

2020-2021cbsechapter 5class10ncertperiodic classificationscience
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      1. Mendeleev was unable to give fixed position to hydrogen and isotopes in the periodic table.
      2. In Mendeleev’s periodic table, the increasing manner of atomic mass of the elements is not always regular from one to its next. It was believed that a more fundamental property than atomic mass could explain periodic properties in a better manner.
      3. It was Henry Moseley who demonstrated that atomic number of an element could explain periodic properties in a better way than atomic mass of an element and arranged the elements in increasing order of their atomic numbers. Then it was found that the various anomalies of Mendeleev’s periodic table were removed by the modern periodic table.

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      1. Proper place for inert gases.
      2. Now elements are arranged according to atomic number instead of atomic mass.
      3. Isotopes problems is solved.
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      • Isotopes problem is solved.
      • Noble gases which are discovered later placed separately.
      • Atomic numbers are now increasing in regular way.
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    4. All the answers are correct.

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    6. Various anomalies of Mendeleev’s Periodic Table removed as follows in the Modern Periodic Table:
      (i) Elements are arranged in the increasing order of their atomic number in Modern Periodic Table, thus there was no need for keeping more than one element in one slot.
      (ii) In Modern Periodic Table there was no problem of the place of isotopes, as isotopes have same atomic mass with different atomic numbers.
      (iii) Elements having same valence electron are kept in same group.
      (iv) Elements having same number of shells were put under the same period.
      (v) Position of hydrogen became clarified in as it is kept in the group with the elements of same valence electrons.

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