Of the following the ion with the largest size is

Options

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

Answer

To solve the question of which ion has the largest size among O²⁻, Na⁺, F⁻, and Al³⁺, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Ions and Their Charges**:
- We have four ions: O²⁻ (oxide ion), Na⁺ (sodium ion), F⁻ (fluoride ion), and Al³⁺ (aluminum ion).

2. **Determine the Number of Electrons**:
- All these ions are isoelectronic, meaning they have the same number of 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).
- Al³⁺ has 10 electrons (13 protons - 3 electrons).

3. **Identify the Atomic Numbers**:
- O has an atomic number of 8.
- F has an atomic number of 9.
- Na has an atomic number of 11.
- Al has an atomic number of 13.

4. **Understand Nuclear Charge**:
- The nuclear charge is determined by the number of protons in the nucleus. A higher nuclear charge means a stronger attraction between the nucleus and the electrons, resulting in a smaller ion size.
- O²⁻ has a nuclear charge of +8.
- F⁻ has a nuclear charge of +9.
- Na⁺ has a nuclear charge of +11.
- Al³⁺ has a nuclear charge of +13.

5. **Compare the Nuclear Charges**:
- Since all ions have the same number of electrons (10), the size of the ions will inversely relate to their nuclear charge.
- The ion with the smallest nuclear charge will be the largest in size.
- O²⁻ has the smallest nuclear charge (+8), followed by F⁻ (+9), Na⁺ (+11), and Al³⁺ (+13).

6. **Conclusion**:
- Therefore, the ion with the largest size is O²⁻.

### Final Answer:
The ion with the largest size is **O²⁻**.