Which of the following electronic configuration in the outermost shell is characterstic of alkali metals?

Options

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

Answer

To determine which electronic configuration in the outermost shell is characteristic of alkali metals, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Alkali Metals**: Alkali metals are located in Group 1 of the periodic table. They include elements like Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), and Cesium (Cs).

2. **Identify the General Electronic Configuration**: The general electronic configuration for alkali metals is \( ns^1 \), where \( n \) represents the principal quantum number corresponding to the outermost shell.

3. **Analyze the Given Configurations**: Look at the options provided in the question and identify which one matches the \( ns^1 \) configuration.

4. **Exclude Other Configurations**:
- If a configuration ends with \( ns^2 \) or \( np^1 \) or any configuration that suggests filling of d or p orbitals, it cannot be characteristic of alkali metals.
- For example, configurations like \( 3d^{10} 4s^1 \) indicate that the d orbital is being filled, which is characteristic of transition metals (d-block elements), not alkali metals.

5. **Select the Correct Configuration**: The only configuration that shows one electron in the outermost s orbital (i.e., \( ns^1 \)) is the characteristic of alkali metals.

### Conclusion:
After analyzing the configurations, the correct answer is the one that follows the \( ns^1 \) pattern.