EDTA has coordination number

Options

A. (a) `3`
B. (b) `4`
C. (c) `5`
D. (d) `6`

Explanation

To determine the coordination number of EDTA (ethylenediaminetetraacetic acid), we need to analyze its structure and how it interacts with metal ions.

### Step-by-Step Solution:

1. **Understand the Structure of EDTA**:
- EDTA is a hexadentate ligand, which means it can form six bonds with a metal ion. It contains two nitrogen atoms and four carboxylate groups (–COO⁻) that can donate electron pairs to the metal.

2. **Identify the Donor Atoms**:
- In EDTA, the donor atoms are:
- 2 Nitrogen (N) atoms
- 4 Oxygen (O) atoms from the carboxylate groups
- Each of these donor atoms can coordinate to a metal ion.

3. **Count the Coordination Sites**:
- Since there are 2 nitrogen atoms and 4 oxygen atoms that can bond to the metal ion, we add these together:
- 2 (from N) + 4 (from O) = 6 coordination sites.

4. **Conclusion**:
- Therefore, the coordination number of EDTA when it binds to a metal ion is 6.

### Final Answer:
The coordination number of EDTA is 6.

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