The complex trioxalatochromate (III) ion exhibits

Options

A. optical isomerism
B. ionization isomerism
C. geometrical isomerism
D. linkage isomerism.

Explanation

To determine the type of isomerism exhibited by the complex trioxalatochromate(III) ion, we can follow these steps:

### Step 1: Identify the complex and its formula
The complex is trioxalatochromate(III). The oxalate ion (C2O4) has a charge of -2, and since there are three oxalate ligands, the total negative charge contributed by the ligands is:
\[ 3 \times (-2) = -6 \]

Since chromium is in the +3 oxidation state, the overall charge of the complex can be calculated as:
\[ \text{Charge of chromium} + \text{Charge from oxalate} = +3 + (-6) = -3 \]

Thus, the formula for the complex is:
\[ \text{Cr(C2O4)3}^{3-} \]

### Step 2: Determine the geometry of the complex
The complex has an octahedral geometry because it is formed by a central metal ion (chromium) surrounded by six donor atoms from three bidentate ligands (oxalate). In an octahedral arrangement, the ligands can occupy positions in various ways.

### Step 3: Analyze possible isomerism
1. **Ionization Isomerism**: This type of isomerism occurs when different ions can be formed from the same complex. In this case, since all ligands are oxalate and there are no counter ions, ionization isomerism is not possible.

2. **Geometrical Isomerism**: This occurs when ligands can be arranged differently in space. However, because all oxalate ligands are identical and bidentate, they cannot form cis or trans isomers.

3. **Linkage Isomerism**: This type occurs when a ligand can coordinate to the metal in different ways. Since oxalate can only coordinate through its two oxygen atoms, linkage isomerism is not applicable here.

4. **Optical Isomerism**: This occurs when a complex can exist in two non-superimposable mirror images (enantiomers). Given that the complex is octahedral with bidentate ligands, it can exhibit optical isomerism.

### Conclusion
The trioxalatochromate(III) ion exhibits **optical isomerism** due to the presence of chiral arrangements of the bidentate oxalate ligands.

### Final Answer
The complex trioxalatochromate(III) ion exhibits **optical isomerism**.

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