What is the total no. of rare earth metals:
What is the total no. of rare earth metals:
17
12
18
14
The Correct Option is A
Solution and Explanation
The correct option is (A): 17
Top Questions on Periodic Classification of Elements
- A metal and a non-metal that exists in liquid state at the room temperature are respectively :
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- Given below are two statements:
Statement (I): The 4f and 5f-series of elements are placed separately in the Periodic table to preserve the principle of classification.
Statement (II): s-block elements can be found in pure form in nature.
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Which one of the following elements is found in the free state in nature?
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Concepts Used:
Classification of Elements & Periodicity in Properties
Since many elements were being discovered in the 19th century and the study of these elements individually was proving difficult, classification of elements was made necessary.
Classification by Johann Dobereiner - German chemist Johann Dobereiner classified certain elements on the basis of their similar properties in the groups of continuing - three elements each. These groups were called ‘triads’. In every triad, the atomic weight of the middle element was equal to the average of the atomic weights of the first and third elements.
Newlands Law of Octaves - The elements were arranged in increasing order of their atomic weights and found that every 8th element shows similarity with the 1st element.
Mendeleev’s Periodic Table - The arrangement of all 63 elements in rows or columns in order of their atomic weight was made by Mendeleev. He left some space for corresponding elements in his periodic table which were not even discovered till then. Although he predicted the properties of those elements through his periodic classification of elements.
Modern Periodic Law - The properties of the elements of the modern periodic law are periodic functions of their atomic numbers.