Question

(3* 10^8 m/ s )(1 5. / 10^8 m /s)​

Answer 1

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Dobereiner arranged the elements in increasing order of atomic masses. He found that the atomic mass of the middle element was approximately equal to the arithmetic mean (average) of the atomic masses of the other two elements of that triad when they are arranged in their increasing order of atomic mass.

So Li=7,K=39

Atomic mass of Na =$\frac{7 + 39}{2} = \frac{46}{2} = 23$

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