Which of the following hydrogen bonds is the strongest ?

Options

A. `O-H- - -F`
B. `O-H- - - H`
C. `F-H- - - F`
D. `O-H - - - O`

Explanation

To determine which hydrogen bond is the strongest among those formed with hydrogen, we need to analyze the electronegativity of the atoms involved in the hydrogen bonds. The primary elements that form hydrogen bonds are nitrogen (N), oxygen (O), and fluorine (F).

### Step-by-Step Solution:

1. **Identify the Elements Involved**:
- The elements that can form hydrogen bonds with hydrogen are nitrogen (N), oxygen (O), and fluorine (F).

2. **Understand Electronegativity**:
- Electronegativity is a measure of an atom's ability to attract and hold onto electrons. The higher the electronegativity, the stronger the attraction for electrons.

3. **List the Electronegativity Values**:
- Hydrogen (H): 2.2
- Nitrogen (N): 3.04
- Oxygen (O): 3.44
- Fluorine (F): 3.98

4. **Calculate the Electronegativity Differences**:
- For the hydrogen bond with oxygen (H-O):
- Difference = |3.44 - 2.2| = 1.24
- For the hydrogen bond with nitrogen (H-N):
- Difference = |3.04 - 2.2| = 0.84
- For the hydrogen bond with fluorine (H-F):
- Difference = |3.98 - 2.2| = 1.78

5. **Compare the Differences**:
- The differences calculated show that H-F has the largest difference (1.78), followed by H-O (1.24), and then H-N (0.84).

6. **Conclusion**:
- Since the strength of a hydrogen bond increases with the difference in electronegativity between the bonded atoms, the hydrogen bond between hydrogen and fluorine (H-F) is the strongest among the three.

### Final Answer:
The strongest hydrogen bond is formed between hydrogen and fluorine (H-F).

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