(a) List two limitations of Newlands' Law of Octaves.
(b) Write the electronic configuration of two elements A and B whose atomic numbers are 20 and 17 respectively. Write the molecular formula of the compound formed when element A reacts with element B. State whether this compound is acidic, basic or neutral. Give reason to justify your answer.

Explanation

### Step-by-Step Text Solution

**(a) Limitations of Newlands' Law of Octaves:**

1. **Limited Applicability:** Newlands' Law of Octaves is applicable only up to calcium (atomic number 20). Beyond calcium, the pattern of properties does not hold true. This means that elements with higher atomic numbers do not follow the same periodic pattern as described by Newlands.

2. **Lack of Scientific Basis:** Newlands arranged elements in order of increasing atomic mass and noted that every eighth element had similar properties, akin to musical octaves. However, there was no scientific explanation for this observation. It was more of a coincidence rather than a scientifically justified classification.

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