Question

Q. State Mendeleev's periodic law. Write achievements of Mendeleev's periodic table.

Answer 1

In 1869, Mendeleev made remarkable contribution to the classification of elements. He gave a law known as periodic law. The law states that the physical and chemical properties of elements are periodic function of their atomic weights. 


Achievements of the Mendeleev's periodic tables are as under:-

1) Systematic study of elements:-

 As the elements having same properties are grouped together so it becomes very useful to remember the properties of large number of elements in a systematic way.

2)  Prediction of new elements:-

 Mendeleev predicted the properties of those missing elements from the known properties of the other elements in the same group. On the basis of this, he named Gallium as Eka-Almunium, Germanium as Eka-Silicon and Scandium as Eka-Boron.

3) Correction of atomic mass:-

 Atomic mass of beryllium was corrected from 13.5 to 9. Atomic mass of indium, gold and platinum were also corrected.

Answer 2

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✔️$\underline{Mendeleev's \:Periodic \:Law}$ states that “The properties of elements are the periodic function of their atomic masses”.

✔️ Achievements of Mendeleev's Periodic Table :-

⏩ Mendeleev left some gaps in his Periodic table. He predicted that some elements will be discovered in future. Mendeleev named them by prefixing a Sanskrit numeral, Eka to the name of preceding elements in the same group.

⏩ When Nobel gas were discovered, they could be placed in a new group without disturbing existing order.

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