Question

What are the drawbacks of law of octaves?
(class 10 CBSE SAMPLE PAPER 2017-18 SCIENCE)

Answer 1

solution:
John Newlands' in 1864 gave the law of octaves.

Drawbacks of law of octaves:

**The law of octaves worked well only for lighter elements and could not be extended to Elements atomic mass  higher than that of Ca (calcium) since after calcium every 8th element did not exhibit properties similar to that of the first.

**Newlands assumed that only 56 elements existed in nature with no scope for discovery of new elements in future. Subsequently quite a large number of new elements discovered whose properties did not fit into Newlands’ law of octaves.

**Newlands assigned one position to 2 elements in order to fit the elements in his periodic table. for example, only one position each was assigned to (Co and Ni) and (Ce and La).

**Newlands placed Cobalt and Nickel in the same column as fluorine(F) ,chlorine(Cl) and bromine(Br) having quite different properties in comparison to Cobalt and Nickel.

**Newlands placed Fe far away from Cobalt(Co) and Nickel(Ni) although Fe resembles Cobalt and Nickel in properties.

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Answer 2

law of octaves was given by newland in 1964 .
drawbacks are ::

1 newlands octaves was only applicable up to calcium . after ca the eight h element don't show the same properties as the first element.

2 newlands assume that only 56 elements will be existed in nature . but soon new element s were created which don not show the same properties.

3 Fe element show the same properties like that of cobalt Nd nickel . but they were put far off in his periodic table .

4 he put some elements more than one in same slot as they were having different properties.


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