Fluorine, the first member of group 17, differs form the other members of group in may respects due to:
i. Very small size
ii. Very high electronegativity
iii. Absence of vacant d-orbitals in the valence shell
iv. Dissociation energy in the molecular form `(X_(2))` is the least
Which of the following bonds is the stronger ?

Options

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

Answer

To determine which bond is stronger among the diatomic halogen molecules (F₂, Cl₂, Br₂, I₂), we need to analyze the factors affecting bond strength, particularly focusing on bond length and the size of the atoms involved.

### Step-by-Step Solution:

1. **Identify the Halogens and Their Bonds**:
The halogens in question are:
- Fluorine (F₂)
- Chlorine (Cl₂)
- Bromine (Br₂)
- Iodine (I₂)

2. **Understand the Trend in Atomic Size**:
As we move down the group from fluorine to iodine, the atomic size increases. This is due to the addition of electron shells:
- Fluorine is the smallest.
- Chlorine is larger than fluorine.
- Bromine is larger than chlorine.
- Iodine is the largest.

3. **Analyze Bond Length**:
Bond length increases as atomic size increases. Thus:
- F-F bond length < Cl-Cl bond length < Br-Br bond length < I-I bond length.

4. **Relate Bond Length to Bond Strength**:
There is an inverse relationship between bond length and bond strength. Generally, shorter bonds are stronger because the atoms are held together more closely.

5. **Consider the Unique Properties of Fluorine**:
- Fluorine has a very small size and high electronegativity, which leads to significant electron-electron repulsion in the F-F bond due to the high density of electron cloud.
- This repulsion weakens the F-F bond despite its short bond length.

6. **Evaluate the Bond Strengths**:
- The bond strength of F-F is actually weaker than expected due to the repulsion.
- Cl-Cl bond, while having a longer bond length than F-F, is stronger because it does not experience the same level of electron repulsion as F-F.

7. **Conclusion**:
Based on the analysis, the bond strength order is:
- Cl-Cl > F-F > Br-Br > I-I
Therefore, the strongest bond among the given options is the Cl-Cl bond.

### Final Answer:
The stronger bond is **Chlorine-Chlorine (Cl-Cl)**.

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