Which has the largest radius?

Options

A. `Co^(3+)`
B. `Mn^(3+)`
C. `Fe^(3+)`
D. `Fe`

Explanation

To determine which of the given elements (CO3+, Mn3+, Fe3+, and Cr3+) has the largest radius, we can follow these steps:

### Step 1: Understand the Concept of Ionic Radius
The ionic radius of an element is influenced by its charge and the number of electrons. Generally, as the positive charge on an ion increases, the radius decreases due to increased effective nuclear charge pulling the electrons closer to the nucleus.

### Step 2: Analyze the Given Ions
We have the following ions to consider:
- CO3+ (Cobalt)
- Mn3+ (Manganese)
- Fe3+ (Iron)
- Cr3+ (Chromium)

### Step 3: Consider the Effective Nuclear Charge
For d-block elements, the shielding effect is poor due to the presence of d-orbitals. As we move from left to right across the d-block, the effective nuclear charge (Z effective) increases, leading to a decrease in ionic radius.

### Step 4: Compare the Elements
- **Cobalt (Co)** is to the left of **Manganese (Mn)**, **Iron (Fe)**, and **Chromium (Cr)** in the periodic table.
- **Manganese (Mn)** is to the left of **Iron (Fe)** and **Chromium (Cr)**.
- As we move from left to right, the ionic radius decreases.

### Step 5: Determine the Order of Ionic Radii
Based on the trend that the ionic radius decreases from left to right, we can arrange the ions in order of decreasing size:
1. CO3+ (Cobalt)
2. Mn3+ (Manganese)
3. Fe3+ (Iron)
4. Cr3+ (Chromium)

### Step 6: Conclusion
Since CO3+ has the largest ionic radius among the given ions, the answer to the question is **CO3+**.

### Final Answer
The element with the largest radius among CO3+, Mn3+, Fe3+, and Cr3+ is **CO3+**.

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