Question

Explain Mendeleev's periodic table and discuss it's advantage's and defects?​

Answer 1

Mendeleev's Periodic Law states that the properties of elements are the periodic function of their relative atomic masses. Mendeleev arranged all 63 elements; which were discovered till his time; in the order of their increasing relative atomic masses in a tabular form. It is known as Mendeleev's Periodic Table. Advantage of Mendeleev Periodic Table :- 1.He left blank Places which help scientist to discover new element 2.When Noble gasses was discovered Hel could add it to periodic table without any major changle 3.He predicted the property of new element Disadvantages :- 1. Couldn't explain position of Hydrogen 2.Couldn't answer the question "Can we have an element with atomic mass 3 between Hydrogen and Helium 3 He placed cobalt before Nickel though Cobalt has more mass..

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Answer 2

Answer:

• Mendeleev Periodic Table :

1. Mendeleev Periodic Table was given by Russian Chemist Dmitri Ivanovich Mendeleev. At that time only 63 elements were discovered.
2. He arranged the elements with similar properties into same vertical columns of the periodic table. He arranged the elements on the basis of their atomic mass and chemical properties. Among chemical properties he treated properties of oxides and hydrides as the basis of classification.
3. He arranged the elements in the increasing order of their atomic masses. He observed that there was periodic occurrence of elements with similar properties.
4. In the periodic table, vertical coulmns are called groups and horizontal rows are called periods.

Mendeleev's Periodic Law states that  “The properties of elements are a periodic function of their atomic masses.”

• Merits of Mendeleev Periodic Table:

1. Some gaps were left in the periodic table for the elements which were not discovered. So that if a certain new element is discovered, it can be placed in a new group without disturbing any existing group.
2. He predicted the presence of three elements and named them as Eka- boron, Eka-aluminium and Eka-silicon. The properties of these three elements were similar to the actual elements which were discovered later. Eka-boron was similar to Scandium, Eka-aluminium was similar to Gallium and Eka-silicon was similar to Germanium.
3. When noble gases were discovered later, they were placed in Mendeleev’s periodic table without disturbing the positions of other elements.

Demerits of Mendeleev Periodic Table:

1. He was unable to determine the position of hydrogen in the periodic table.
2. The increase in atomic mass was not regular while moving from one element to another. Hence, the number of elements yet to be discovered was not predictable.
3. Discovery of isotopes of elements violated Mendeleev’s periodic law.

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