Periodic Table and PeriodicitymediumMCQ SINGLE

The atomic weight of element is and that of element is . If , , and form a Dobereiner's triad, what Periodic Table and Periodicity Chemistry Question

Question

The atomic weight of element $X$ is $35.5$ and that of element $Z$ is $127$. If $X$, $Y$, and $Z$ form a Dobereiner's triad, what is the predicted atomic weight of the intermediate element $Y$?

Answer: B

💡 Solution & Explanation

According to Dobereiner's Law of Triads, the atomic weight of the middle element is approximately the arithmetic mean of the atomic weights of the first and third elements. Atomic weight of $Y = \frac{35.5 + 127}{2} = \frac{162.5}{2} = 81.25$. This corresponds to the $Cl, Br, I$ triad.

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