Chemistry · Modern periodic law and present form of the periodic table
If three elements and form a Dobereiner's triad and atomic weights of and are 9
If three elements \( X, Y, \) and \( Z \) form a Dobereiner's triad and atomic weights of \( X \) and \( Z \) are 9 and 40 respectively then the atomic weight of the element \( Y \) is approximately:
- A. 24.
- B. 49
- C. 34.5
- D. 29
Step-by-step solution
According to Dobereiner's law of triads, the atomic weight of the middle element (Y) is approximately the arithmetic mean of the atomic weights of the other two elements (X and Z). Thus, atomic weight of Y = (9 + 40)/2 = 49/2 = 24.5, which is approximately 24.
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