Halogen with highest electron affinity is

Options

A. F
B. Cl
C. Br
D. I

Answer

To determine which halogen has the highest electron affinity, we will analyze the properties of the halogens and their electron affinity values systematically. The halogens we will consider are Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I).

### Step-by-Step Solution:

1. **Understanding Electron Affinity**:
- Electron affinity is defined as the energy change that occurs when an electron is added to a neutral gaseous atom. If energy is released, the electron affinity is negative, indicating a favorable process.

2. **Halogen Electron Configuration**:
- All halogens have the general electron configuration of \( ns^2 np^5 \), meaning they have 7 valence electrons and require one more electron to complete their octet, achieving stability.

3. **Trends in Electron Affinity**:
- As we move down the group from Fluorine to Iodine, the atomic size increases. This increase in size affects the effective nuclear charge experienced by the added electron.

4. **Effective Nuclear Charge**:
- The effective nuclear charge is inversely related to the distance from the nucleus. A smaller atomic radius means that the nucleus can exert a stronger attractive force on the added electron.

5. **Comparison of Halogens**:
- **Fluorine (F)**: Although it is the smallest atom, the high electron-electron repulsion among the 7 valence electrons in Fluorine makes it less favorable for it to gain an additional electron.
- **Chlorine (Cl)**: Chlorine has a larger atomic radius than Fluorine, but it has less electron-electron repulsion, allowing it to accommodate an additional electron more easily.
- **Bromine (Br)** and **Iodine (I)**: As we go further down, the atomic size increases, and the effective nuclear charge decreases, making it less favorable for these atoms to gain an electron.

6. **Conclusion**:
- Chlorine has the highest electron affinity among the halogens. While Fluorine has a smaller size, the repulsion between its electrons makes it less favorable for gaining an electron. Chlorine, with its larger size and lower repulsion, can accommodate an additional electron more effectively.

### Final Answer:
The halogen with the highest electron affinity is **Chlorine (Cl)**.