Which of the following electronic configuration in the outermost two shells is characteristic of the alkaline earth metals?

Options

A. `(n-1)s^(2)p^(6),ns^(2)underline((n-1)s^(2)p^(6))underline(ns^(2))`
B. `(n-1)s^(2)p^(6)d^(10),ns^(2) underline((n-1)s^(2)p^(6)d)underline(ns^(2))`
C. `(n-1)s^(2)p^(6),ns^(2)np^(1)underline((n-1)s^(2)p^(6)ns^(2)np^(1))`
D. `(n-1)s^(2)p^(6),ns^(2)np^(2)underline((n-1)s^(2)p^(6)ns^(2)np^(2))`.

Answer

To determine which electronic configuration in the outermost two shells is characteristic of alkaline earth metals, we need to analyze the given options based on the known electronic configuration of alkaline earth metals.

### Step-by-Step Solution:

1. **Understand the Electronic Configuration of Alkaline Earth Metals**:
- Alkaline earth metals are found in Group 2 of the periodic table. Their general electronic configuration can be represented as \( [Noble Gas] ns^2 \), where \( n \) is the principal quantum number of the outermost shell. This means they have two electrons in their outermost s subshell.

2. **Examine Each Option**:
- **Option 1**: \( n-1 s^2 p^6 ns^2 \)
- This configuration indicates that the outermost shell has \( ns^2 \), which is characteristic of alkaline earth metals. This option is correct.

- **Option 2**: \( n-1 s^2 p^6 d^{10} ns^2 \)
- This configuration includes \( d \) electrons, indicating that it belongs to a transition metal, not an alkaline earth metal. This option is incorrect.

- **Option 3**: \( n-1 s^2 p^6 ns^2 np^1 \)
- The presence of \( np^1 \) in the outermost shell indicates that this configuration belongs to a p-block element, not an alkaline earth metal. This option is incorrect.

- **Option 4**: \( n-1 s^2 p^6 ns^2 np^2 \)
- Similar to option 3, the presence of \( np^2 \) indicates that this configuration belongs to a p-block element. This option is also incorrect.

3. **Conclusion**:
- The only configuration that matches the characteristic of alkaline earth metals is **Option 1**: \( n-1 s^2 p^6 ns^2 \).

### Final Answer:
The electronic configuration characteristic of alkaline earth metals is **Option 1: \( n-1 s^2 p^6 ns^2 \)**.