Q1. What is Mendeleev periodic law? write any three important aspects.
Q2. Write any three limitations of mendeleev periodic law.
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Answer:
1.) Main features of Mendeleev's Periodic Table:
(a) There are seven horizontal rows in the periodic table.
(b) In a given period, there is a regular gradation in the properties of elements from left to right.
(c) There are eight vertical columns in the periodic table. These are named as groups.
2.) Limitations of the Mendeleev periodic table are listed below. Elements with large differences in properties were included in the same group. ... No proper position could be given to the element hydrogen. In the periodic table, the location of hydrogen is uncertain.
Answer:
1) In Mendeleev’s periodic table, elements were arranged on the basis of the fundamental property, atomic mass, and chemical properties. During Mendeleev’s work, only 63 elements were known.
He observed that elements were arranged in the increasing order of atomic mass and there was the periodic occurrence of elements with similar properties.
In Mendeleev periodic table, vertical columns in the periodic table and horizontal row in the periodic table were named as groups and period respectively.
Some gaps were left for the elements yet to be discovered. Thus, if a certain new element is discovered, it can be placed in a new group without disturbing any existing group.
2) He was unable to locate hydrogen in the periodic table.
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.
Later on, isotopes of elements were found which violated Mendeleev’s periodic law.
Explanation: