Coordination number of calcium is six in .

Options

A. `[Mg(EDTA)]^(2-)`
B. `MgC_(2)O_(4)`
C. `Mg[(C_(2)O_(4))_(2)]^(2-)`
D. `MgSO_(4).4H_(2)O`

Answer

To determine the coordination number of calcium in the given coordination compound, we will analyze the options provided in the question. The coordination number refers to the number of ligand donor atoms that are bonded to the central metal atom.

### Step-by-Step Solution:

1. **Understanding Coordination Number**:
- The coordination number is defined as the total number of ligand atoms that are directly bonded to the central metal atom in a coordination complex.

2. **Identifying the Ligands**:
- We need to look at the ligands present in the options given. Common ligands include EDTA, oxalate, and water.

3. **Analyzing Each Option**:
- **Option A: Mg(EDTA)**: EDTA (ethylenediaminetetraacetic acid) is a hexadentate ligand, meaning it can donate six pairs of electrons (one from each donor atom) to the central metal ion (Mg). Therefore, the coordination number here is 6.
- **Option B: Mg(oxalate)**: Oxalate is a bidentate ligand, which means it can donate two pairs of electrons. If we have two oxalate ligands, the maximum coordination number would be 4 (2 from each oxalate). Thus, this option does not have a coordination number of 6.
- **Option C: MgSO4**: In this case, sulfate acts as a monodentate ligand, contributing only one bonding site. Thus, the coordination number here is not 6.
- **Option D: Mg(H2O)6**: Water is a monodentate ligand, and if there are six water molecules coordinated to magnesium, the coordination number is 6.

4. **Conclusion**:
- The coordination number of calcium in the compound with EDTA is 6, as it can coordinate through multiple donor sites. Therefore, the correct answer is the option that includes EDTA.

### Final Answer:
The coordination number of calcium is six in the compound with EDTA.