Electronic configuration of few elements are given below. Mark the incorrect match.

Options

A. `1s^(2)2s^(2)2p^(5)`, Most electronegative element
B. `1s^(2)2s^(2)2p^(3)`, An element, belonging to 3 period and 5 group
C. `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(8)4s^(2)`, A d - block element
D. `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)`, An element from 18 group

Answer

To solve the problem, we need to analyze the electronic configurations given and determine which one does not match the description provided. Let's go through the options step by step.

### Step 1: Analyze the first option
- **Configuration:** 1s² 2s² 2p⁵
- **Element:** This configuration corresponds to Fluorine (F), which is indeed the most electronegative element.
- **Conclusion:** This is a correct match.

### Step 2: Analyze the second option
- **Configuration:** 1s² 2s² 2p³
- **Description:** An element belonging to the 3rd period and 5th group.
- **Analysis:** The configuration indicates that the highest principal quantum number (n) is 2, which means this element belongs to the 2nd period, not the 3rd. Therefore, it cannot belong to the 3rd period.
- **Conclusion:** This is an incorrect match.

### Step 3: Analyze the third option
- **Configuration:** 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s²
- **Description:** A d-block element.
- **Analysis:** The presence of the 3d subshell indicates that this element is indeed a d-block element.
- **Conclusion:** This is a correct match.

### Step 4: Analyze the fourth option
- **Configuration:** 1s² 2s² 2p⁶ 3s² 3p⁶
- **Description:** A group 18 element.
- **Analysis:** This configuration corresponds to Argon (Ar), which is a noble gas and belongs to group 18. It is completely filled.
- **Conclusion:** This is a correct match.

### Final Conclusion
The only incorrect match is the second option, which states that the configuration 1s² 2s² 2p³ belongs to the 3rd period and 5th group.

### Answer:
**The incorrect match is option 2.**

---