Which of the following properties among halongens decrease(s) from fluorine to iodine?

Options

A. Electronegativity
B. Bond energy
C. Ionisation energy
D. Electron affinity

Answer

To determine which properties among halogens decrease from fluorine to iodine, we will analyze the properties one by one.

### Step 1: Analyze Electronegativity
- **Definition**: Electronegativity is the tendency of an atom to attract electrons in a chemical bond.
- **Trend**: As we move down the group from fluorine (F) to iodine (I), the atomic radius increases. This increase in size means that the distance between the nucleus and the outermost electrons also increases, which reduces the nucleus's ability to attract electrons.
- **Conclusion**: Electronegativity decreases from fluorine to iodine.

### Step 2: Analyze Bond Energy
- **Definition**: Bond energy is the energy required to break a bond between two atoms.
- **Trend**: The bond energy is influenced by the size of the atoms. Fluorine atoms are smaller and can form stronger bonds due to their high electronegativity. As we go down the group, the size of the atoms increases, leading to weaker bonds because the atoms are further apart.
- **Conclusion**: Bond energy decreases from fluorine to iodine.

### Step 3: Analyze Ionization Energy
- **Definition**: Ionization energy is the energy required to remove an electron from an atom in its gaseous state.
- **Trend**: Similar to electronegativity, as the atomic radius increases down the group, the outermost electrons are further from the nucleus and are held less tightly. Therefore, it requires less energy to remove an electron.
- **Conclusion**: Ionization energy decreases from fluorine to iodine.

### Step 4: Analyze Electron Affinity
- **Definition**: Electron affinity is the energy change that occurs when an electron is added to a neutral atom.
- **Trend**: The electron affinity generally decreases down the group, but the trend can vary due to the stability of the resulting anions. However, for halogens, the general trend is that electron affinity decreases from fluorine to iodine.
- **Conclusion**: Electron affinity also decreases from fluorine to iodine.

### Final Conclusion
The properties that decrease from fluorine to iodine are:
1. Electronegativity
2. Bond Energy
3. Ionization Energy
4. Electron Affinity

Thus, all the properties mentioned (electronegativity, bond energy, and ionization energy) decrease as we move from fluorine to iodine.

---