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)`
B. `(n-1)s^(2)p^(6)d^(10)ns^(2)`
C. `(n-1)s^(2)p^(2)ns^(2)p^(1)`
D. none of these

Answer

To determine the electronic configuration characteristic of alkaline earth metals, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Alkaline Earth Metals**:
Alkaline earth metals belong to Group 2 of the periodic table. This group includes elements like Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra).

2. **Understand Electronic Configuration**:
The electronic configuration of an element describes the distribution of electrons in its atomic orbitals. For alkaline earth metals, the outermost shell will have two electrons in the s subshell.

3. **General Electronic Configuration**:
The general electronic configuration for alkaline earth metals can be expressed as:
- For the outermost shell (n): ns²
- For the previous shell (n-1): (n-1)s² (which can also include filled p orbitals, e.g., (n-1)p⁶).

4. **Example of Magnesium**:
Taking Magnesium (Mg) as an example:
- Its electronic configuration is 1s² 2s² 2p⁶ 3s².
- Here, the outermost shell (n=3) has 2 electrons in the 3s subshell, and the previous shell (n=2) has a complete configuration of 2s² 2p⁶.

5. **Analyzing Options**:
Now, let's analyze the given options:
- **Option A**: n-1 s² p⁶ and ns². This corresponds to the configuration of alkaline earth metals, where the (n-1) shell is filled (n-1)s² (p⁶) and the outermost shell has ns².
- **Option B**: n-1 s² p⁶ d¹⁰. This is incorrect because alkaline earth metals do not have d electrons in their outermost configuration.
- **Option C**: s² p² and ns. This is also incorrect as it does not follow the expected configuration of alkaline earth metals.

6. **Conclusion**:
The correct electronic configuration characteristic of alkaline earth metals is represented by **Option A**: n-1 s² p⁶ and ns².

### Final Answer:
**The characteristic electronic configuration of alkaline earth metals is represented by Option A: n-1 s² p⁶ and ns².**