Question

Differentiate between the arrangement of elements in Mendeleev’s periodic table and Modern periodic table.

Answer 1

	Mendeleev’s periodic table	Modern periodic table.
1	The elements were arranged according to  increasing atomic masses.	The elements were arranged according to increasing atomic masses.
2	Position of isotopes was not justified.	There was no problem in the placing of isotopes.
3	Position of hydrogen was not justified because it resembles both with alkali metals and halogens.	Hydrogen has been given a unique position due to its resemblance with alkalis and halogens.