Flourine has more negative electron gain enthalpy than chlorine.(T/F)

Answer

To determine whether the statement "Fluorine has more negative electron gain enthalpy than chlorine" is true or false, we can analyze the concept of electron gain enthalpy (or electron affinity) and the electronic configurations of fluorine and chlorine.

### Step-by-Step Solution:

1. **Understanding Electron Gain Enthalpy**:
- Electron gain enthalpy refers to the energy change when an electron is added to a neutral atom in the gas phase. A more negative value indicates a greater tendency to gain an electron.

2. **Identify the Atomic Numbers**:
- Fluorine (F) has an atomic number of 9.
- Chlorine (Cl) has an atomic number of 17.

3. **Determine the Electronic Configurations**:
- The electronic configuration of Fluorine:
- F: 1s² 2s² 2p⁵
- The electronic configuration of Chlorine:
- Cl: 1s² 2s² 2p⁶ 3s² 3p⁵

4. **Analyze the Electron Gain Process**:
- When an electron is added to fluorine (2p⁵), the added electron experiences greater repulsion due to the smaller size of the 2p orbital. This results in a less favorable (less negative) electron gain enthalpy.
- In contrast, when an electron is added to chlorine (3p⁵), the 3p orbital is larger, and the added electron experiences less repulsion, making it easier for chlorine to gain an electron.

5. **Conclusion**:
- Since chlorine has a larger atomic radius and less electron-electron repulsion when gaining an electron, it has a more negative electron gain enthalpy compared to fluorine.
- Therefore, the statement "Fluorine has more negative electron gain enthalpy than chlorine" is **False**.

### Final Answer:
**False** - Chlorine has more negative electron gain enthalpy than fluorine.