Which of the following has highest bond strength :

Options

A. HI
B. HCl
C. HF
D. HBr

Answer

To determine which of the given compounds (HI, HCl, HF, HBr) has the highest bond strength, we can follow these steps:

### Step 1: Understand the Compounds
The compounds in question are hydrogen halides: HI (hydrogen iodide), HCl (hydrogen chloride), HF (hydrogen fluoride), and HBr (hydrogen bromide). Each of these compounds consists of hydrogen bonded to a halogen.

### Step 2: Analyze the Halogens
The halogens in the compounds are:
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br)
- Iodine (I)

As we move down the group in the periodic table from fluorine to iodine, the size of the atoms increases. This is due to the addition of electron shells.

### Step 3: Consider Bond Strength
Bond strength is influenced by the size of the atoms involved in the bond:
- Smaller atoms can form stronger bonds because the overlap of their atomic orbitals is more effective.
- Larger atoms have a greater distance between their nuclei, leading to weaker bonds.

### Step 4: Compare the Bond Strengths
- **HF**: Fluorine is the smallest halogen, leading to a very strong bond with hydrogen.
- **HCl**: Chlorine is larger than fluorine, resulting in a weaker bond than HF.
- **HBr**: Bromine is larger than chlorine, leading to an even weaker bond than HCl.
- **HI**: Iodine is the largest halogen, resulting in the weakest bond among the four.

### Step 5: Conclusion
Based on the analysis, HF has the highest bond strength due to the small size of fluorine, which allows for a strong overlap of orbitals with hydrogen.

### Final Answer
The compound with the highest bond strength is **HF (hydrogen fluoride)**.

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