Question

Distinguish between the arrangement of elements in Mendeleev's periodic table and Modern periodic table. Which of the two arrangements of elements is better and why?

Answer 1

Mendleev's Periodic Table	Modern Periodic Table
1. Elements are arranged in the increasing order of atomic masses.	1. Elements are arranged in the increasing order of atomic numbers.
2. Position of hydrogen could not be explained.	2. Hydrogen is placed above alkali metals.
3. Elements are placed in 7 groups and 6 periods.	3. Elements are placed in 18 groups and 7 periods.
4. Metals and nonmetals are not separated.	4. Metals and non-metals are separated.
5. Elements with similar property are placed.	5. Elements with same valence shell are present in the same period while elements having the same number of valence electrons are present in the same group.

The modern periodic table arrangement is better because elements are arranged in increasing order of atomic numbers.