If the elements , , and form a Dobereiner's triad and the atomic weights of and are and respectively — Periodic Table and Periodicity Chemistry Question
Question
If the elements $A$, $B$, and $C$ form a Dobereiner's triad and the atomic weights of $A$ and $C$ are $7$ and $39$ respectively, what is the exact predicted atomic weight of the middle element $B$?
Answer: 23
💡 Solution & Explanation
By Dobereiner's Law of Triads, the atomic weight of the middle element is the arithmetic mean of the first and third elements. Atomic weight of $B = \frac{7 + 39}{2} = \frac{46}{2} = 23$. This represents the Lithium (7), Sodium (23), Potassium (39) triad.
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