Which of the following has the highest ionic radius?

Options

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

Explanation

To determine which of the given ions has the highest ionic radius, we can follow these steps:

### Step 1: Identify the Ions
We have the following ions to consider:
1. F⁻ (Fluoride ion)
2. B³⁺ (Boron ion)
3. O²⁻ (Oxide ion)
4. Li⁺ (Lithium ion)

### Step 2: Classify the Ions
Next, we classify these ions into cations and anions:
- Anions: F⁻ and O²⁻
- Cations: B³⁺ and Li⁺

### Step 3: Understand Ionic Radius Trends
We know that:
- Anions (negatively charged ions) are larger than their neutral atoms because they gain electrons, which increases electron-electron repulsion.
- Cations (positively charged ions) are smaller than their neutral atoms because they lose electrons, which decreases electron-electron repulsion.

### Step 4: Compare the Anions
Now, we will compare the two anions:
- F⁻ has a single negative charge.
- O²⁻ has a double negative charge.

### Step 5: Analyze Charge and Size
The greater the negative charge on an ion, the larger the ionic radius due to increased electron-electron repulsion:
- F⁻ has one negative charge, while O²⁻ has two negative charges.
- Therefore, O²⁻ will have a larger ionic radius than F⁻ because it has more electrons and greater repulsion among them.

### Step 6: Conclusion
Since the cations (B³⁺ and Li⁺) are smaller than their neutral atoms, they will have smaller ionic radii compared to the anions. Between the two anions, O²⁻ has the highest ionic radius.

Thus, the ion with the highest ionic radius is **O²⁻** (Option C).

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