Question

what is the difference in the approach between the mendeleevs periodic law and the modern periodic law​

Answer 1

Mendeleev

Mendeleev's periodic law states- "The properties of the elements of the periodic table are functions of their atomic masses"

Mendeleev arranged the elements in increasing order of atomic mass

However the drawbacks were

1) He wasn't able to position Hydrogen

2) He was not able to accommodate isotopes in the periodic table

3) There were irregular gaps in between some consecutive elements. It was impossible to predict how many elements would lie between any two.

Modern Periodic Table

The modern periodic law, proposed by Henry Mosley, states that - "The properties of the elements of the periodic table are functions of their atomic numbers"

This proposition was able to correct all the defects of Mendeleev's periodic table, because atomic mass was taken as the fundamental criterion, not atomic mass.

Answer 2

Answer:

• Mendeleev's periodic table

1. elements are arranged in increasing order of their atomic masses.
2. It is not divided into any blocks.
3. There are 8 groups.
4. Isotopes could not be placed properly.

• Modern periodic table

1. Elements are arranged in increasing order of their atomic numbers.
2. It is divided into four blocks, namely s-block,p-block,d-block and f-block.
3. There are 18 groups.
4. Isotopes occupy the same position as the element.

Hope you understood mate!!!