Question

Explain the comparison of Mendeleev and Modern periodic table?

Answer 1

Comparison of Mendeleev and Modern periodic table

S.No.	Characteristic	Mendeleev Periodic Table	Modern Periodic Table
1.	Arrangement of elements	In Mendeleev's periodic table elements are arranged in increasing order of their atomic weight.	In the modern periodic table, elements are arranged according to their increasing atomic number.
2.	Position of isotopes (elements with the same atomic number but with different mass numbers)	In Mendeleev's periodic table isotopes of every element were given a different place	In the modern periodic table, isotopes were placed with the element itself.
3.	Number of elements	Mendeleev’s periodic table was for the arrangement of 63 elements known at that time.	The modern table accommodates all the 118 natural and synthetic elements.
4.	Uneven grouping of elements	In Mendeleev’s periodic table, coinage metals like copper, silver, and gold are grouped with very active alkali metals. Manganese metal was grouped with halogens in the seventh group.	This defect was rectified in the Modern periodic table.
5	Anomaly in Mendeleev's table	In Mendeleev’s periodic table the element pairs, Argon-potassium, cobalt-nickel, tellurium-iodine, and thorium and protactinium, elements with higher atomic mass precede the element with lower atomic mass. It is the right place for them but is against Mendeleev’s periodic law.	The modern periodic table rectifies the defects of Mendeleev’s periodic table.
6	Number of periods and groups	Mendeleev's periodic table was divided into 7 periods and 8 groups and each group is further subdivided into subgroups.	The modern periodic table is divided into 18 groups and 7 periods.