Which of the following statements are correct?

Options

A. F is the most electronegative and Cs is the most electropositive element
B. The ionization energy of halogens decreses from F to I
C. The electron affinity of Cl is higher than that of F thorugh their electronegativities are in the reverse order
D. The electron affinity of noble gases in almost zero

Answer

To determine which of the statements provided are correct, we will analyze each statement one by one based on our knowledge of periodic properties.

### Step-by-Step Solution:

1. **Statement 1: Fluorine is the most electronegative element and cesium is the most electropositive element.**
- **Analysis**: Fluorine is indeed the most electronegative element in the periodic table due to its high effective nuclear charge and small atomic size, which allows it to attract electrons strongly. Cesium, being an alkali metal, has the lowest ionization energy in its group, making it the most electropositive element.
- **Conclusion**: This statement is **true**.

2. **Statement 2: The ionization energy of halogens decreases from fluorine to iodine.**
- **Analysis**: Ionization energy is the energy required to remove the most loosely bound electron from an atom. As we move down the group from fluorine to iodine, the atomic size increases due to the addition of electron shells, which leads to a decrease in ionization energy.
- **Conclusion**: This statement is **true**.

3. **Statement 3: The electron affinity of chlorine is higher than that of fluorine, though their electronegativities are in the reverse order.**
- **Analysis**: Electron affinity is the energy released when an electron is added to a neutral atom. While fluorine is more electronegative than chlorine, its small size leads to significant electron-electron repulsion when an additional electron is added, resulting in a lower electron affinity compared to chlorine, which is larger and experiences less repulsion.
- **Conclusion**: This statement is **true**.

4. **Statement 4: The electron affinity of noble gases is almost zero.**
- **Analysis**: Noble gases have a complete valence shell, making them very stable and unlikely to gain additional electrons. Therefore, their tendency to accept electrons is minimal, resulting in an electron affinity that is close to zero.
- **Conclusion**: This statement is **true**.

### Final Conclusion:
All four statements are correct. Therefore, the answer is that **statements 1, 2, 3, and 4 are all true**.