Which one among the following ions, is smallest in size

Options

A. `N^(3-)`
B. `O^(2-)`
C. `F^(-)`
D. `Na^(+)`

Answer

To determine which ion among N³⁻, O²⁻, F⁻, and Na⁺ is the smallest in size, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Ions and Their Electron Configuration**:
- N³⁻ has 10 electrons (7 protons + 3 extra electrons).
- O²⁻ has 10 electrons (8 protons + 2 extra electrons).
- F⁻ has 10 electrons (9 protons + 1 extra electron).
- Na⁺ has 10 electrons (11 protons - 1 electron).

2. **Determine the Number of Protons**:
- N³⁻: 7 protons
- O²⁻: 8 protons
- F⁻: 9 protons
- Na⁺: 11 protons

3. **Calculate the E/P Ratio**:
- The E/P ratio is calculated by dividing the number of electrons (E) by the number of protons (P).
- For N³⁻: E/P = 10/7 ≈ 1.43
- For O²⁻: E/P = 10/8 = 1.25
- For F⁻: E/P = 10/9 ≈ 1.11
- For Na⁺: E/P = 10/11 ≈ 0.91

4. **Analyze the E/P Ratios**:
- The smaller the E/P ratio, the smaller the ionic size.
- From our calculations, we see:
- N³⁻: 1.43
- O²⁻: 1.25
- F⁻: 1.11
- Na⁺: 0.91

5. **Conclusion**:
- Since Na⁺ has the smallest E/P ratio (0.91), it is the smallest ion among the given options.

### Final Answer:
Na⁺ is the smallest ion in size.