Hexadentate ligand out of the following is :

Options

A. `C_2O_4^(2-)`
B. EDTA
C. `NH_2CH_2CH_2NH_2`
D. `NO_2^(-)`

Explanation

To determine which of the given ligands is hexadentate, we need to analyze each option based on the number of donor atoms they possess. A hexadentate ligand can attach to a central metal atom through six donor atoms.

### Step-by-Step Solution:

1. **Understanding Denticity**:
- Denticity refers to the number of donor atoms in a ligand that can coordinate to a central metal atom. A ligand is termed hexadentate if it has six donor atoms.

2. **Analyzing the Options**:
- **C2O4 (Oxalate)**: This ligand has two carboxylate groups (–COO⁻) and can coordinate through two oxygen atoms from each carboxylate group. Therefore, it is bidentate (2 donor atoms).
- **EDTA (Ethylenediaminetetraacetate)**: This ligand has four acetate groups and two nitrogen atoms. Each acetate group can donate one oxygen atom, and the two nitrogen atoms can donate one lone pair each. Thus, EDTA has a total of 6 donor atoms (4 oxygen + 2 nitrogen), making it hexadentate.
- **NH2CH2CH2NH2 (Ethylenediamine)**: This ligand has two nitrogen atoms that can donate lone pairs, making it bidentate (2 donor atoms).
- **NO2 (Nitrite)**: This ligand can coordinate through one nitrogen or one oxygen atom, making it monodentate (1 donor atom).

3. **Conclusion**:
- Among the given options, only EDTA (Ethylenediaminetetraacetate) is hexadentate because it has six donor atoms.

### Final Answer:
The hexadentate ligand out of the following is **EDTA (Ethylenediaminetetraacetate)**.

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