The least stable ion among the following is

Options

A. `Li^(o+)`
B. `B^(ɵ)`
C. `C^(ɵ)`
D. `Be^(ɵ)`

Explanation

To determine the least stable ion among the given options (Li⁺, B⁻, C⁻, and Be⁻), we will analyze the electronic configurations of each ion and assess their stability based on their configurations.

### Step-by-Step Solution:

1. **Identify the Electronic Configuration of Each Ion:**
- **Li⁺:** Lithium (Li) has the atomic number 3. Its electronic configuration is 1s² 2s¹. When it loses one electron to form Li⁺, its configuration becomes 1s², which is the same as helium (He), a noble gas. This configuration is stable.

- **B⁻:** Boron (B) has the atomic number 5. Its electronic configuration is 1s² 2s² 2p¹. When it gains one electron to form B⁻, its configuration becomes 1s² 2s² 2p². This configuration is not particularly stable because it does not achieve a noble gas configuration and is not half-filled or fully filled.

- **C⁻:** Carbon (C) has the atomic number 6. Its electronic configuration is 1s² 2s² 2p². When it gains one electron to form C⁻, its configuration becomes 1s² 2s² 2p³. This configuration is stable because it is half-filled (2p³), which is generally more stable.

- **Be⁻:** Beryllium (Be) has the atomic number 4. Its electronic configuration is 1s² 2s². When it gains one electron to form Be⁻, its configuration becomes 1s² 2s² 2p¹. This configuration is less stable because it moves from a fully filled 2s subshell to a configuration that is not particularly stable.

2. **Assess Stability:**
- Li⁺ is stable (noble gas configuration).
- B⁻ is less stable than Li⁺ but more stable than Be⁻.
- C⁻ is stable (half-filled configuration).
- Be⁻ is the least stable since it disrupts the stable configuration of beryllium.

3. **Conclusion:**
Based on the analysis, the least stable ion among the given options is **Be⁻**.

### Final Answer:
The least stable ion among the following is **Be⁻**.