Which one of the following pairs of atoms/atom-ion have identical ground state configuration?

Options

A. `Li^(+)` and `He^(+)`
B. `Cl^(-)` and Ar
C. Na and K
D. `F^(+)` and Ne.

Explanation

To determine which pair of atoms or ions have identical ground state configurations, we need to analyze the electron configurations of each option provided. Let's break down the process step by step:

### Step 1: Identify the Atoms/Ions
We need to analyze the following pairs:
1. Lithium ion (Li⁺) and Helium ion (He⁺)
2. Chlorine ion (Cl⁻) and Argon (Ar)
3. Sodium (Na) and Potassium (K)
4. Fluorine ion (F⁺) and Neon (Ne)

### Step 2: Determine the Electron Configuration
1. **Lithium ion (Li⁺)**:
- Atomic number of Li = 3
- Li has 3 electrons. As Li⁺ loses one electron, it has 2 electrons.
- Configuration: 1s²

2. **Helium ion (He⁺)**:
- Atomic number of He = 2
- He has 2 electrons. As He⁺ loses one electron, it has 1 electron.
- Configuration: 1s¹

3. **Chlorine ion (Cl⁻)**:
- Atomic number of Cl = 17
- Cl has 17 electrons. As Cl⁻ gains one electron, it has 18 electrons.
- Configuration: 3s² 3p⁶

4. **Argon (Ar)**:
- Atomic number of Ar = 18
- Ar has 18 electrons.
- Configuration: 3s² 3p⁶

5. **Sodium (Na)**:
- Atomic number of Na = 11
- Na has 11 electrons.
- Configuration: 1s² 2s² 2p⁶ 3s¹

6. **Potassium (K)**:
- Atomic number of K = 19
- K has 19 electrons.
- Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

7. **Fluorine ion (F⁺)**:
- Atomic number of F = 9
- F has 9 electrons. As F⁺ loses one electron, it has 8 electrons.
- Configuration: 1s² 2s² 2p⁶

8. **Neon (Ne)**:
- Atomic number of Ne = 10
- Ne has 10 electrons.
- Configuration: 1s² 2s² 2p⁶

### Step 3: Compare Configurations
Now, we compare the configurations:
- **Li⁺ (1s²)** and **He⁺ (1s¹)**: Different configurations.
- **Cl⁻ (3s² 3p⁶)** and **Ar (3s² 3p⁶)**: Identical configurations.
- **Na (1s² 2s² 2p⁶ 3s¹)** and **K (1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹)**: Different configurations.
- **F⁺ (1s² 2s² 2p⁶)** and **Ne (1s² 2s² 2p⁶)**: Identical configurations.

### Conclusion
The pair that has identical ground state configurations is **Chlorine ion (Cl⁻)** and **Argon (Ar)**, both having the configuration **3s² 3p⁶**.

### Final Answer
**B. Chlorine ion (Cl⁻) and Argon (Ar)** have identical ground state configurations.