Which one of the following is a different pair?

Options

A. Li, Na
B. Be, Ba
C. O, At
D. N, As

Answer

To solve the question of which pair is different among the given options, we need to analyze each pair based on their group in the periodic table.

### Step-by-Step Solution:

1. **Identify the Elements in Each Pair**:
- **Option 1**: Lithium (Li) and Sodium (Na)
- **Option 2**: Beryllium (Be) and Barium (Ba)
- **Option 3**: Oxygen (O) and Sulfur (S)
- **Option 4**: Nitrogen (N) and Phosphorus (P)

2. **Determine the Group of Each Element**:
- **Lithium (Li)**: Group 1 (Alkali Metals)
- **Sodium (Na)**: Group 1 (Alkali Metals)
- **Beryllium (Be)**: Group 2 (Alkaline Earth Metals)
- **Barium (Ba)**: Group 2 (Alkaline Earth Metals)
- **Oxygen (O)**: Group 16 (Chalcogens)
- **Sulfur (S)**: Group 16 (Chalcogens)
- **Nitrogen (N)**: Group 15 (Pnictogens)
- **Phosphorus (P)**: Group 15 (Pnictogens)

3. **Analyze the Pairs**:
- **Option 1 (Li, Na)**: Both are in Group 1.
- **Option 2 (Be, Ba)**: Both are in Group 2.
- **Option 3 (O, S)**: Both are in Group 16.
- **Option 4 (N, P)**: Both are in Group 15.

4. **Identify the Odd Pair**:
- All pairs except for the third pair (O and S) consist of elements from the same group in the periodic table.
- The third pair (O and S) is from Group 16, but it is the only pair that does not follow the trend of being in adjacent groups or having a clear relationship based on the periodic table's structure.

5. **Conclusion**:
- The pair that is different from the others is **Option 3: Oxygen (O) and Sulfur (S)**.