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How Could the Modern Periodic Table Remove Various Anomalies of Mendeleev’S Periodic Table? - Science

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

How could the modern periodic law remove various anomalies of Mendeleev's periodic table? Explain with examples.

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Solution 1

Various anomalies of Mendeleev’s Periodic Table removed as follows in the Modern Periodic Table:

→ 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.

→ In Modern Periodic Table there was no problem of the place of isotopes, as isotopes have same atomic mass with different atomic numbers.

→ Elements having same valence electron are kept in same group.

→ Elements having same number of shells were put under the same period.
→ Position of hydrogen became clarified in as it is kept in the group with the elements of same valence electrons.

Solution 2

As the modern periodic law is based on the atomic numbers of elements, all the anomalies of Mendeleev's periodic table are removed. For example:

1. The position of isotopes could be explained, which the Mendeleev's periodic table failed to explain. As all the isotopes of an element have the same atomic number, they can be placed under the same group in a periodic table.
For example:  Cl-35 and Cl-36, which are the isotopes of Chlorine with the same atomic number 17, they can be placed in the same group of the periodic table.

2. Mendeleev could not explain why cobalt was placed before nickel. This problem was solved by the modern periodic law. The atomic numbers of cobalt and nickel are 27 and 28 respectively. Hence, cobalt with a lower atomic number was placed before nickel in the modern periodic table.

Concept: Merits and Demerits of Mendeleev’s Periodic Table
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NCERT Class 10 Science
Chapter 5 Periodic Classification of Elements
Q 1 | Page 90
Lakhmir Singh Class 10 Chemistry (Science)
Chapter 5 Periodic Classification Of Elements
Q 29.3 | Page 283

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