Question

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Answer 1

Answer:

1st answer- Newland's Law of Octaves states that when Elements are arranged in increasing order of Atomic Mass, the properties of every eighth Element starting from any Element are a repetition of the properties of the starting Element. Law of Octaves was true only for Elements up to Calcium.

2nd answer - (c) 78 the atomic mass of element Z is 78

according to Dobereiners low of treads atomic mass Y

X+Y

____

2

therefore , Z= 78

Explanation:

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Answer 2

Answer:

1. Calcium

2. 78

3. dobereiner laws of triad: when elements are arranged in order of increasing atomic masses groups of three elements (triads)having similar chemical properties are obtained. the atomic mass of the middle elements of the triads being equal to the Arithmetic mean on the atomic masses of the other two elements.

dobereiner could find only three triads: i.e total of 9 elements only. however the total number of elements were more than that of those encompassed in Dobereiner triads.

4. newland arranged the known elements in increasing order of atomic masses. he found that every eighth element had properties similar to that of first one. he compared it to the Octaves and thus it is called newlands law of octaves .

5. the major limitations were: it applied to only lighter elements having atomic masses upto 40 u i.e up to calcium. the first and eighth element after calcium did not have the same properties. only 63 elements for considered to exist in nature and no new elements would be discovered in the future.

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