Generated by claude-sonnet-4-6 · 2026-06-15 06:52 · grounding rag
Model Answer
(a) Newland's Law of Octaves:
When elements are arranged in increasing order of their atomic masses, every eighth element has properties similar to the first element, just like the eighth note of a musical octave.
(b) Dobereiner's Triads:
Dobereiner grouped elements with similar properties into sets of three (triads), where the atomic mass of the middle element was approximately the arithmetic mean of the other two.
Example: In the triad Li (7), Na (23), K (39) — atomic mass of Na = (7+39)/2 = 23. ✓
(c) Limitations:
- Newland's Law of Octaves: It was applicable only up to calcium; elements discovered later did not fit the pattern.
- Dobereiner's Triads: Only a few elements could be grouped into triads; the law could not cover all known elements.
Explanation
- The question is from Chapter 5 (Periodic Classification of Elements), not the provided passages — answer is based on standard NCERT Class 10 Science content.
- For (b), always give a specific triad with atomic masses and show the mean calculation — examiners expect the numerical verification.
- For (c), one limitation each is enough (½ mark each); keep them distinct — one for Octaves, one for Triads.
- Do not mix up the two scientists' contributions.