Which of the following set of elements obeyes Newland’s octave rule -

Options

A. Na, K, Rb
B. F, Cl, Br
C. Be, Mg, Ca
D. B, Al, Ga

Answer

To determine which set of elements obeys Newland’s Octave Rule, we need to analyze the provided options based on the rule itself. Newland's Octave Rule states that when elements are arranged in increasing order of their atomic masses, every eighth element has similar physical and chemical properties.

### Step-by-Step Solution:

1. **Understand Newland's Octave Rule**:
- Newland's Octave Rule suggests that if elements are arranged according to their increasing atomic masses, the first element will have similar properties to the eighth element.

2. **Evaluate the Options**:
- We will analyze each option to see if they follow the rule.

3. **Option 1: Sodium (Na), Potassium (K), Rubidium (Rb)**:
- Sodium (Na) is the first element, and if we count eight elements from Sodium, we get Rubidium (Rb). However, Potassium (K) does not follow the trend as it is not the eighth element from Sodium. Therefore, this option does not obey Newland's Octave Rule.

4. **Option 2: Fluorine (F), Chlorine (Cl), Bromine (Br)**:
- Fluorine (F) is the first element. Counting eight elements from Fluorine, we would not land on Bromine (Br) as it does not follow the sequence correctly. Hence, this option also does not obey Newland's Octave Rule.

5. **Option 3: Beryllium (Be), Magnesium (Mg), Calcium (Ca)**:
- Beryllium (Be) is the first element. Counting eight elements from Beryllium, we find that Magnesium (Mg) and Calcium (Ca) follow the sequence correctly. Thus, this option obeys Newland's Octave Rule.

6. **Option 4: Boron (B), Aluminium (Al), Gallium (Ga)**:
- Boron (B) is the first element. Counting eight elements from Boron, we do not reach Gallium (Ga) as it does not fit the sequence correctly. Therefore, this option does not obey Newland's Octave Rule.

7. **Conclusion**:
- The only set of elements that obeys Newland’s Octave Rule is **Option 3: Beryllium (Be), Magnesium (Mg), Calcium (Ca)**.

### Final Answer:
**Option 3: Beryllium (Be), Magnesium (Mg), Calcium (Ca)** obeys Newland's Octave Rule.

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