Which halogen is known to cause the reaction given below: `2Cu^(2+)+4X^(-)rarrCu_(2)X_(2)(s)+X_(2)`

Options

A. Only Iodine
B. All halogens
C. Only chlorine
D. only Bromine

Answer

To determine which halogen causes the reaction \(2Cu^{2+} + 4X^{-} \rightarrow Cu_{2}X_{2}(s) + X_{2}\), we need to analyze the stability of the resulting compound \(Cu_{2}X_{2}\) based on the size of the cation \(Cu^{2+}\) and the anion \(X^{-}\).

### Step-by-Step Solution:

1. **Identify the Reaction Components:**
The reaction involves copper ions (\(Cu^{2+}\)) and halide ions (\(X^{-}\)). The product is a solid compound \(Cu_{2}X_{2}\) along with diatomic halogen gas \(X_{2}\).

2. **Consider the Halogens:**
The halogens in question are fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). We need to evaluate their ionic sizes:
- Fluorine: \(F^{-}\) (small anion)
- Chlorine: \(Cl^{-}\) (medium-sized anion)
- Bromine: \(Br^{-}\) (larger anion)
- Iodine: \(I^{-}\) (largest anion)

3. **Analyze the Stability of \(Cu_{2}X_{2}\):**
The stability of the compound \(Cu_{2}X_{2}\) depends on the interaction between the small cation \(Cu^{2+}\) and the anion \(X^{-}\). A smaller cation is generally more stable with a similarly sized anion.

4. **Evaluate Each Halogen:**
- **Fluorine:** The small size of \(F^{-}\) would lead to a stable compound with \(Cu^{2+}\), but \(Cu_{2}F_{2}\) is not commonly formed.
- **Chlorine:** \(Cl^{-}\) is larger than \(F^{-}\) but smaller than \(Br^{-}\) and \(I^{-}\). However, \(Cu_{2}Cl_{2}\) is not a typical product in this context.
- **Bromine:** \(Br^{-}\) is larger than \(Cl^{-}\) and may form \(Cu_{2}Br_{2}\), but it is not as stable as iodine.
- **Iodine:** \(I^{-}\) is the largest anion. The combination of a small cation \(Cu^{2+}\) with a large anion \(I^{-}\) leads to instability in the compound \(Cu_{2}I_{2}\), resulting in the release of \(I_{2}\) gas.

5. **Conclusion:**
The only halogen that leads to the formation of the compound \(Cu_{2}X_{2}\) while also releasing \(X_{2}\) gas is iodine. Therefore, the correct answer is that only iodine causes the reaction.

### Final Answer:
**Only iodine is known to cause the reaction given below.**