Which of the following is the most powerful reducing agent ?

Options

A. `F^(-)`
B. `Cl^(-)`
C. `Br^(-)`
D. `I^(-)`

Explanation

To determine which of the following species is the most powerful reducing agent among F⁻, Cl⁻, Br⁻, and I⁻, we need to analyze their ability to donate electrons. A reducing agent is a substance that can easily lose electrons and thus reduce another substance.

### Step-by-Step Solution:

1. **Understanding Reducing Agents**:
- A reducing agent is a species that donates electrons to another species, causing the other species to be reduced. The more easily a species can donate electrons, the stronger of a reducing agent it is.

2. **Analyzing the Given Species**:
- The species we are considering are F⁻ (fluoride), Cl⁻ (chloride), Br⁻ (bromide), and I⁻ (iodide).

3. **Comparing Sizes and Electronegativity**:
- The size of the ions increases as we move down the group in the periodic table:
- F⁻ < Cl⁻ < Br⁻ < I⁻
- Electronegativity decreases as we move down the group:
- F > Cl > Br > I

4. **Evaluating I⁻ (Iodide)**:
- I⁻ is the largest ion among the given options. Its larger size means that the attraction between the nucleus and the outermost electrons is weaker, making it easier for I⁻ to lose an electron. Therefore, I⁻ can donate electrons more readily than the others.

5. **Evaluating F⁻ (Fluoride)**:
- F⁻, on the other hand, is the smallest ion with the highest electronegativity. This means it holds onto its electrons tightly and does not easily donate them, making it a poor reducing agent.

6. **Conclusion**:
- Based on the analysis, I⁻ is the most powerful reducing agent among the options provided because it can donate electrons easily due to its larger size and lower electronegativity compared to the other halides.

### Final Answer:
The most powerful reducing agent among the given options is **I⁻ (iodide)**.

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