The most stable ion is .

Options

A. `[Fe(C_(2)O_(4))_(3)]^(3-)`
B. `[Fe(CI)_(6)]^(3-)`
C. `[Fe(H_(2)O)_(6)]^(3+)`
D. `[Fe(SCN)_(6)]^(3-)`

Explanation

To determine the most stable ion among the given complexes, we need to analyze the types of ligands present in each option and their respective denticities.

### Step-by-Step Solution:

1. **Understanding Ligands and Denticity**:
- Ligands can be classified based on the number of donor atoms they have.
- **Monodentate ligands** have one donor atom (e.g., NH3, Cl-, H2O, SCN-).
- **Bidentate ligands** have two donor atoms (e.g., oxalate, C2O4^2-).

2. **Identifying the Ligands in the Options**:
- Option 1: Oxalate (C2O4^2-) - Bidentate ligand
- Option 2: Chlorine (Cl-) - Monodentate ligand
- Option 3: Water (H2O) - Monodentate ligand
- Option 4: Thiocyanate (SCN-) - Monodentate ligand

3. **Analyzing Stability**:
- Bidentate ligands like oxalate can form chelate rings when they bind to a central metal ion. This ring formation provides additional stability compared to monodentate ligands, which do not form such rings.
- The chelating effect is a significant factor in the stability of coordination compounds. Bidentate and polydentate ligands create more stable complexes due to the formation of chelate rings.

4. **Conclusion**:
- Since option 1 contains a bidentate ligand (oxalate), it is more stable than the complexes in options 2, 3, and 4, which contain monodentate ligands.
- Therefore, the most stable ion among the given complexes is from option 1 (oxalate).

### Final Answer:
The most stable ion is from option 1 (oxalate).