Question

what are the limitations of mendeleev's classification?​

Answer 1

Answer:

Limitations of the Mendeleev periodic table are listed below.

Elements with large differences in properties were included in the same group. for example, hard metals like copper and silver were included along with soft metals like sodium and potassium.

No proper position could be given to the element hydrogen. In the periodic table, the location of hydrogen is uncertain. It was put with alkali metals within 1A class, but certain hydrogen properties are close to those of halogens. So, it can also be put for halogens in the band.

The increasing order of atomic mass was not strictly followed throughout. For example in cobalt and nickel & Tellurium and Indium.

As isotopes are atoms of the same element having different atomic masses, they should have been given different positions while arranging them in the order of atomic mass. But this was not done.

Explanation:

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Answer 2

Answer:

Limitations are :

• Position of hydrogen: Hydrogen is placed in Group IA. However, it actually resembles the elements of Group-IA (alkali metals ) as well as the elements of Group VII-A (halogens ). Thus, the position of hydrogen in the periodic table is not clear.
• Position of isotopes: On the basis of atomic weight , various isotopes of the same elements should be assigned different places in the periodic table. Mendeleev could not provide separate places for isotopes.
• Position of lanthanides and actinides: Fourteen elements following Lanthanum(known aslanthanidesorrare earths) and the fourteen elements following Actinium (known asactinides or transuranic elements) have not been provided separate and proper places in the Mendeleev 's table, rather they have been placed in two rows at the bottom of the table.
• Dissimilar elements placed together: Noble metals like Cu, Ag and Au are placed along with chemically dissimilar alkali metals in Group I . Similarly, Mn possessing very few similarities with halogens have been placed in VII group.
• Similar elements separated: IN Mendeleev 's periodic table, certain chemically similar elements such as copper and mercury ; gold and platinum have been placed in different groups.
• Anomalous pairs: IN the Mendeleev 's Table based on atomic weight, the positions of certain pairs , e.g. Argon( at. wt = 39.94) and potassium ( at. wt = 39.1) : Cobalt( at wt =58.93 ) and nickel ( at wt = 58.71 ) ; Tellurium at wt = 127.60) and iodine (atomic weight = 126.90 ) would be reversed. In other words, certain pairs of elements are misfit in the periodic table, if atomic weight is the basis of classification.

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