Which does not exist ?

Options

A. `[C Cl_6]^(2-)`
B. `[Si Cl_6]^(2-)`
C. `[Ge F_6]^(2-)`
D. `[Sn Cl_6]^(2-)`

Explanation

To solve the question "Which does not exist?" regarding the compounds of the 4th group elements (carbon, silicon, germanium, and tin), we will analyze the electronic configurations and the ability of these elements to form certain compounds.

### Step-by-Step Solution:

1. **Identify the Elements**: The elements in the 4th group of the periodic table are carbon (C), silicon (Si), germanium (Ge), and tin (Sn).

2. **Examine the Electronic Configuration**:
- **Carbon (C)**: The electronic configuration is \(1s^2 2s^2 2p^2\). Carbon has only 2 electron shells and does not have any d-orbitals available.
- **Silicon (Si)**: The electronic configuration is \(1s^2 2s^2 2p^6 3s^2 3p^2\). Silicon has 3 shells and can utilize d-orbitals.
- **Germanium (Ge)**: The electronic configuration is \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4p^2\). Germanium has 4 shells and can utilize d-orbitals.
- **Tin (Sn)**: The electronic configuration is \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4p^6 5s^2 5p^2\). Tin has 5 shells and can utilize d-orbitals.

3. **Determine Coordination Numbers**:
- Coordination number refers to the number of atoms or ions surrounding a central atom in a complex or compound.
- Carbon can only form compounds with a coordination number of 4 because it lacks empty d-orbitals to accommodate more than 4 bonds.
- Silicon, germanium, and tin can form compounds with higher coordination numbers (like 6) because they have empty d-orbitals available for bonding.

4. **Conclusion**: Since carbon cannot form a compound with a coordination number of 6 (for example, \(CCl_6^{2-}\)), it does not exist. Therefore, the answer to the question is that the compound \(CCl_6^{2-}\) does not exist.

### Final Answer:
**The compound \(CCl_6^{2-}\) does not exist.**

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