Per NCERT §3.2, Dobereiner's LAW OF TRIADS (1829) said which of the following about a triad of three elements?
ATriads always have the same colour
BThe atomic weight of the middle element is approximately the AVERAGE of the other two — e.g. Na (23) ≈ ½(Li 7 + K 39)
CEvery third element has identical chemistry
DTriads share the same atomic number
Answer & Solution
Correct answer: B. The atomic weight of the middle element is approximately the AVERAGE of the other two — e.g. Na (23) ≈ ½(Li 7 + K 39)
Per NCERT §3.2 Table 3.1, Dobereiner's triad: atomic weight of middle element ≈ average of the other two. Li/Na/K, Ca/Sr/Ba, Cl/Br/I.
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