Which of the following electronic configuration represents the most metallic element ?

Options

A. `[He] 2s^(1)`
B. `[Ne] 3s^(1)`
C. `[Ar] 4s^(1)`
D. `[Kr] 5s^(1)`

Answer

To determine which electronic configuration represents the most metallic element, we need to analyze the given options based on their positions in the periodic table and the concept of metallic character.

### Step-by-Step Solution:

1. **Identify the Elements from the Electronic Configurations:**
- Option 1: Helium (2s1) - This is Lithium (Li).
- Option 2: Neon (3s1) - This is Sodium (Na).
- Option 3: Argon (4s1) - This is Potassium (K).
- Option 4: Krypton (5s1) - This is Rubidium (Rb).

2. **Understand the Trend of Metallic Character:**
- Metallic character increases as you move down a group in the periodic table. This is due to the increase in atomic size, which makes it easier for the atom to lose its outermost electron.

3. **Analyze the Group of Elements:**
- All the elements listed (Li, Na, K, Rb) belong to Group 1 (alkali metals).
- As we go down the group from Lithium to Rubidium, the atomic size increases.

4. **Determine the Most Metallic Element:**
- Since Rubidium (Rb) is the lowest in the group, it has the largest atomic size among the given options.
- The larger atomic size means that it is easier for Rubidium to lose its outermost electron, which corresponds to a higher metallic character.

5. **Conclusion:**
- Therefore, the electronic configuration that represents the most metallic element is **Krypton (5s1)**, which corresponds to **Rubidium (Rb)**.

### Final Answer:
The most metallic element is represented by the electronic configuration **Krypton (5s1)**, which corresponds to **Rubidium (Rb)**.

---