Question

Case-based question

In the year 1817, a German chemist, arranged certain elements with similar properties (both

physical and chemical) in groups of three. The basis of the arrangement was the atomic masses

of the elements. In a particular group, the elements (e.g., A,B,C) with atomic masses 7,23 and

39 respectively were arranged in order of increasing atomic masses and the atomic mass of the

middle element (B)was almost the mean or the average of the atomic masses of the first and

third elements i.e.; A and C.

(i) Which of the following scientist had proposed such a classification of elements?

(a) Henry Mosely (b) Dimitri Mendeleev

(c) John Newlands (d) Johann Dobereiner

(ii) What could be the elements A,B and C?

(a) Calcium, Strontium and Barium (b) Lithium, Sodium and Potassium

(c)Lithium, Sodium and Calcium (d) Nitrogen, Calcium and Iodine

(iii) The three imaginary elements X,Y & Z represent elements according to the given law. If the

atomic mass of element X is 14 and that of Y is 46, then the atomic mass of element Z will be:

(a) 78 (b) 32 (c) 18 (d) 60

(iv) What is the limitation of law discussed in the given paragraph?

(a) This law could not explain the position of isotopes

(b) This law proved to be true for elements only up to calcium

(c) This law could define a total of 9 elements only

(d) This law could not define the position of Hydrog​en​

Answer 1

ans-1=(d)-johann dobereiner.

2-(b) lithium,strontium,potassium

3-(d)=60

4-(c)

Answer 2

Answer:

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Explanation:

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