Question

1) From the given three categories A, B and C pick the one which
forms Dobereiner's Triads.
() Why did Mendeleev placed elements of category A, B and C in three
different groups ?
(iii) Is Newland law of octaves applicable to all the three categories ?
Give reason to justify your answer.​

Answer 1

Answer:

1) Category A fullfill dobrenier trade

2) Because mandeleev Aaranged elements on the basis of chemical properties or on the basis of Atomic mass .

3) No, Newlands law of octaves is only applicable on category A . Because it is only successful till Calcium .

Answer 2

The answer to the above questions are:

1. Dobereiner's Triads were a group of three elements that shared physical similarities as well as chemical properties. He stated that the mean of the mass of the first and third elements is the mass of the second element. In Category A, the mean of the mass of Li(7), Na(23) and K(39) is 23 which is the mass of the second element Na.
2. Mendeleev placed elements based on their atomic weight, unlike Dobereiner. Hence the elements were now placed in groups depending upon their atomic mass and not the arithmetic mean of two elements.
3. Since Newland Octaves was approved only for elements till Calcium. He could not apply his theory to the rest of the elements. Since only Category A consists of all elements before calcium, Newland's Law of Octaves is applicable to only Category A.