Q1. [3]
⚠ Periodic Classification of Elements [2022 syllabus - removed in 2023 CBSE rationalisation; retained for pre-2023 board questions] — Formative only — not assessed in the Board exam (per CBSE 2026-27 curriculum)
Included in the syllabus but assessed only formatively; not in the year-end Board exam. [source: Course Structure, Unit I + Note for Teachers pt.1]In the following table, some elements have been arranged in a certain pattern. Identify the periodic law with which the given table is associated. List two important features and two anomalies of the above periodic law.
Previously asked in CBSE board exam
2022 31/3/1 Q10
Generated by claude-sonnet-4-6 · 2026-06-15 06:52 · grounding rag
Model Answer
The table is associated with Newlands' Law of Octaves.
Two Important Features:
- When elements are arranged in increasing order of atomic masses, every eighth element has properties similar to the first, like the eighth note of a musical scale (octave).
- It was the first attempt to classify elements systematically, covering elements from hydrogen (H) to thorium (Th).
Two Anomalies:
- It worked only up to calcium; after calcium, every eighth element did not possess properties similar to the first element.
- Newlands adjusted two elements in one slot (e.g., Co and Ni, Ce and La) to fit the pattern, which was not justified.
Explanation
The musical note pattern in the table is the direct clue — Newlands compared element repetition to musical octaves. Examiners expect you to name the law clearly, then give exactly two features and two anomalies (each as a distinct point). Common mistakes: confusing this with Mendeleev's law, or giving only one anomaly. Stick to the points above for full marks.
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