Which of the following statements is not correct about the electron gain enthalpy?

Options

A. In general, the electron gain enthalpy becomes less negative in going from top to bottom In a group.
B. The electron gain enthalpy becomes less negative in a period from left to right.
C. The elements having stable configuration like noble gases have large positive electron gain enthalpies.
D. Noble gases have large positive electron gain enthalpies.

Answer

To determine which statement about electron gain enthalpy is not correct, let's analyze each statement based on the trends and principles of electron gain enthalpy.

### Step-by-Step Solution:

1. **Understanding Electron Gain Enthalpy**:
- Electron gain enthalpy refers to the amount of energy released when an electron is added to a neutral atom in the gaseous state.

2. **Trend in a Group (Top to Bottom)**:
- As we move down a group in the periodic table, the atomic size increases.
- This increase in size leads to a decrease in the effective nuclear charge experienced by the outermost electrons.
- Therefore, it becomes more difficult to add an electron, and the electron gain enthalpy becomes **less negative** (or more positive).

3. **Trend in a Period (Left to Right)**:
- As we move across a period from left to right, the atomic size decreases due to an increase in effective nuclear charge.
- This makes it easier to add an electron, and thus the electron gain enthalpy becomes **more negative**.

4. **Noble Gases**:
- Noble gases have a complete octet, making them very stable.
- When an electron is added to a noble gas, it goes into a higher energy level, resulting in a large positive electron gain enthalpy.

5. **Analyzing the Statements**:
- **Statement A**: "In general, the electron gain enthalpy becomes less negative in going from top to bottom in a group."
- This statement is **correct**.
- **Statement B**: "The electron gain enthalpy becomes less negative in period from left to right."
- This statement is **incorrect** because it should become more negative as we move from left to right.
- **Statement C**: "The electron having stable configuration like noble gases have large positive gain enthalpies."
- This statement is **correct**.
- **Statement D**: "Noble gases have large positive gain enthalpies."
- This statement is also **correct**.

6. **Conclusion**:
- The only incorrect statement is **Statement B**.

### Final Answer:
The statement that is not correct about the electron gain enthalpy is **Statement B**.

---