Correct order of Ionic radii :-

Options

A. `Ti^(4+) lt Mn^(7+)`
B. `Cr^(+6) gt Cr^(3+)`
C. `K^(+) gt Cl^(-) `
D. `P^(3+) gt P^(+5)`

Answer

To determine the correct order of ionic radii for the given ions, we need to understand the relationship between ionic charge and ionic size. Here is a step-by-step solution:

### Step 1: Understand Ionic Radii
Ionic radii refer to the size of an ion in a crystal lattice. The size of an ion is influenced by its charge:
- Cations (positively charged ions) are smaller than their parent atoms because they lose electrons, which reduces electron-electron repulsion.
- Anions (negatively charged ions) are larger than their parent atoms because they gain electrons, increasing electron-electron repulsion.

### Step 2: Analyze the Charge Effect
The ionic radius is inversely proportional to the charge of the ion:
- Higher positive charge → smaller ionic radius
- Lower positive charge or negative charge → larger ionic radius

### Step 3: Evaluate Each Option
Let’s evaluate the given options one by one:

1. **Ti⁴⁺ vs Mn⁷⁺**:
- Ti⁴⁺ has a +4 charge, and Mn⁷⁺ has a +7 charge.
- Since Mn⁷⁺ has a higher positive charge, it will have a smaller ionic radius than Ti⁴⁺.
- **This option is incorrect.**

2. **Cr⁶⁺ vs Cr³⁺**:
- Cr⁶⁺ has a +6 charge, and Cr³⁺ has a +3 charge.
- Cr⁶⁺ will have a smaller ionic radius than Cr³⁺ due to the higher charge.
- **This option is incorrect.**

3. **K⁺ vs Cl⁻**:
- K⁺ is a cation with a +1 charge, while Cl⁻ is an anion with a -1 charge.
- Cations are smaller than anions, so K⁺ will have a smaller ionic radius than Cl⁻.
- **This option is incorrect.**

4. **P³⁺ vs P⁵⁺**:
- P³⁺ has a +3 charge, and P⁵⁺ has a +5 charge.
- P³⁺ will have a larger ionic radius than P⁵⁺ because it has a lower positive charge.
- **This option is correct.**

### Conclusion
The correct order of ionic radii among the given ions is:
- P³⁺ > P⁵⁺

Thus, the final answer to the question is **Option D**.

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