Which of the following orders of ionic radii is correctly represented?

Options

A. `H^(-) gt H^(+) gt H`
B. `Na^(+)gtF^(-) gt O^(2-)`
C. `O^(2-)gtF^(-) gt Na^(+)`
D. `AI^(3+) gt Mg^(2+) gt N^(3-)`.

Answer

To determine the correct order of ionic radii among the given options, we need to analyze the ionic species based on their effective nuclear charge and the number of electrons they possess. Here’s a step-by-step breakdown of the solution:

### Step 1: Analyze H⁻, H, and H⁺
- **Species**: H⁻ (hydride ion), H (neutral hydrogen), H⁺ (hydrogen ion).
- **Protons**: All three species have 1 proton.
- **Electrons**:
- H⁻ has 2 electrons (1 proton + 1 extra electron).
- H has 1 electron.
- H⁺ has 0 electrons.
- **Effective Nuclear Charge**: As the number of electrons decreases, the effective nuclear charge (Z effective) increases because the same number of protons is attracting fewer electrons.
- **Size Order**: The ionic radii order will be H⁻ > H > H⁺.

### Step 2: Analyze Na⁺, F⁻, and O²⁻
- **Species**: Na⁺ (sodium ion), F⁻ (fluoride ion), O²⁻ (oxide ion).
- **Protons**:
- Na⁺ has 11 protons.
- F⁻ has 9 protons.
- O²⁻ has 8 protons.
- **Electrons**: All three species have 10 electrons.
- **Effective Nuclear Charge**:
- Na⁺ (11 protons) has the highest effective nuclear charge, thus it will be the smallest.
- F⁻ (9 protons) has a lower effective nuclear charge than Na⁺, so it is larger.
- O²⁻ (8 protons) has the lowest effective nuclear charge, making it the largest.
- **Size Order**: The ionic radii order will be O²⁻ > F⁻ > Na⁺.

### Step 3: Analyze Al³⁺, Mg²⁺, and N³⁻
- **Species**: Al³⁺ (aluminum ion), Mg²⁺ (magnesium ion), N³⁻ (nitride ion).
- **Protons**:
- Al³⁺ has 13 protons.
- Mg²⁺ has 12 protons.
- N³⁻ has 7 protons.
- **Electrons**: All three species have 10 electrons.
- **Effective Nuclear Charge**:
- Al³⁺ (13 protons) has the highest effective nuclear charge, making it the smallest.
- Mg²⁺ (12 protons) is larger than Al³⁺ but smaller than N³⁻.
- N³⁻ (7 protons) has the lowest effective nuclear charge, making it the largest.
- **Size Order**: The ionic radii order will be N³⁻ > Mg²⁺ > Al³⁺.

### Conclusion
Based on the analysis:
- The correct order of ionic radii is found in option 3: O²⁻ > F⁻ > Na⁺ and N³⁻ > Mg²⁺ > Al³⁺ is also correct.

### Final Answer
The only correct order of ionic radii is found in option 3.

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