Why Moseley's classification failed Related: NCERT EXEMPLAR - Periodic Classification of Elements?

Question

Why Moseley's classification failed Related:  NCERT EXEMPLAR - Periodic Classification of Elements?

Answer

Limitations of Moseley's periodic table are

The position of Hydrogen is still not clear although it is generally grouped with alkali metals.

There is no place for lanthanoids and actinides in the main body of the periodic table.This challenges the modern periodic law that 'the properties of the elements are the periodic function of their atomic number'. because after the element with atomic number 57, 72 is the next element .Similarly after 89,104.

Answer

The limitations of modern periodic table or Henry moseley's periodic table are :-

i) It could not provide a proper placement of hydrogen....

ii) no place to isotopes of various elements is given....

Answer

Position of hydrogen and istopes not given

Answer

Https://edurev.page.link/SXYcep3mAgqjw6vG8

Answer

Classification was failed becoz-->>

When Moseley arranged the elements in the periodic table by their number of protons rather than their atomic weights, the flaws in the periodic table that had been making scientists uncomfortable for decades simply disappeared

Answer

Moseley's Classification and its Failure

Introduction:
Moseley's classification, also known as the Modern Periodic Law, was proposed by Henry Moseley in 1913. It was an improvement over Mendeleev's periodic table and successfully arranged the elements in increasing order of atomic numbers. However, Moseley's classification had certain limitations that led to its failure.

1. No provision for isotopes:
- Moseley's classification did not account for the existence of isotopes.
- Isotopes are atoms of the same element with different atomic masses.
- Since Moseley's classification was solely based on atomic numbers, isotopes of the same element were placed in different positions in the periodic table, leading to confusion and inconsistency.

2. Incorrect placement of hydrogen:
- Moseley placed hydrogen in Group 1, along with alkali metals.
- However, hydrogen exhibits properties of both alkali metals and halogens.
- Placing hydrogen in a specific group based on its chemical behavior is difficult due to its unique characteristics, making its placement uncertain in Moseley's classification.

3. Lack of proper explanation for periodicity:
- Moseley's classification provided a systematic arrangement of elements based on atomic numbers, but it did not offer an explanation for the periodic trends observed.
- It failed to explain why certain elements show similar chemical properties and why there are periodic variations in physical and chemical properties across the periodic table.

4. Incomplete representation of elements:
- Moseley's classification did not include the entire range of elements known at that time.
- Some elements were yet to be discovered, and their properties were not accounted for in Moseley's classification.
- This limited the usefulness of the periodic table as a comprehensive tool for understanding the properties and behavior of all elements.

Conclusion:
Moseley's classification, although an improvement over Mendeleev's periodic table, had significant limitations that led to its failure. It did not consider isotopes, incorrectly placed hydrogen, lacked an explanation for periodicity, and had an incomplete representation of elements. These drawbacks paved the way for further advancements in periodic classification, such as the modern periodic table that incorporates all the elements and provides a more comprehensive understanding of their properties and behavior.

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