Consider the following standard electrode potentials (`E^(@)` in volts) in aqueous solution:
`{:(underline("Element"), M^(3+)//M, M^(+)//M), ("Al", -1.66, + 0.55), (TI, +1.26, -0.34):}`
Based on these data, which of the following statements is correct ?

Options

A. `Tl^(3+)` is more stable than `Al^(3+)`
B. `Al^(+)` is more stable than `Al^(3+)`
C. `Tl^(3+)` is more stable than `Al^(3+)`
D. `Tl^(+)` is more stable than `Al^(+)`

Answer

To solve the problem, we will analyze the standard electrode potentials provided for Aluminium (Al) and Thallium (Tl) and determine which statements about their stability are correct based on these potentials.

### Step-by-Step Solution:

1. **Understanding Standard Electrode Potentials**:
- The standard electrode potential (E°) indicates the tendency of a species to gain electrons (be reduced). A higher (more positive) E° value means a greater tendency to be reduced, while a lower (more negative) E° value indicates a lesser tendency to be reduced.

2. **Identifying the Given Data**:
- For Aluminium (Al):
- \( \text{Al}^{3+} + 3e^- \rightarrow \text{Al} \) has \( E° = -1.66 \, \text{V} \) (reduction potential).
- \( \text{Al}^+ + e^- \rightarrow \text{Al} \) has \( E° = +0.55 \, \text{V} \) (reduction potential).
- For Thallium (Tl):
- \( \text{Tl}^{3+} + 3e^- \rightarrow \text{Tl} \) has \( E° = +1.26 \, \text{V} \) (reduction potential).
- \( \text{Tl}^+ + e^- \rightarrow \text{Tl} \) has \( E° = -0.34 \, \text{V} \) (reduction potential).

3. **Analyzing Stability**:
- **For \( \text{Al}^{3+} \)**:
- The potential is \( -1.66 \, \text{V} \), indicating that it is less stable compared to \( \text{Tl}^{3+} \) which has a potential of \( +1.26 \, \text{V} \).
- **For \( \text{Al}^+ \)**:
- The potential is \( +0.55 \, \text{V} \), indicating it is more stable than \( \text{Tl}^+ \) which has a potential of \( -0.34 \, \text{V} \).

4. **Conclusion**:
- From the analysis:
- \( \text{Tl}^+ \) is more stable than \( \text{Al}^+ \) because \( \text{Tl}^+ \) has a more negative reduction potential.
- \( \text{Al}^{3+} \) is more stable than \( \text{Tl}^{3+} \) because it has a more negative reduction potential.

5. **Final Statement**:
- The correct statement based on the given data is: **Thallium ion (Tl\(^+\)) is more stable than Aluminium ion (Al\(^+\))**.