Can you explain the merits and demerits of dobereiner's and newland law of octaves?

also explain both of them?

Newlands Law of Octaves has many limitations, which are discussed below.

• This law was not applicable throughout the arrangement. It was applicable only till calcium.

• Newlands assumed that only 56 elements would exist in nature and believed that no more elements would be discovered. However, several elements were discovered in the following years. These elements did not follow the Law of Octaves.

• The positions of cobalt and nickel could not be explained according to Newlands Law of Octaves. He kept cobalt and nickel in the same slot. They were also placed in the same column as fluorine and chlorine, which have completely different properties.

• The properties of iron are similar to those of cobalt and nickel. However, iron was placed away from them in a different column.

Merits of Newlands Law of Octaves____

• Newlands law of octave provided a basis for the classification of element on the basis of having similar properties into groups of elements.
• The arrangement of elements in tabular form was provided by Newlands law of Octaves.
• Newlands law of octave was the first logically basis on the atomic weight.

Demerits of dobereiner’s triads system:

1. - This system fails because it does not hold good for all the elements discovered till date time. It is limited to only few elements.
2. - It does not completely explain the complete properties of elements like valency, oxidation state of elements which have variable oxidation state like phosphorus showing trivalent and pentavalent nature.
3. - It does not fit to transition elements.

The only advantage of Dobereiner’s research was that it made chemists look at elements in terms of groups of elements with similar chemical and physical properties. This eventually led to rigorous classification of elements and the modern periodic table of elements, as we now know it, was discovered.