The order of strength of hydrogen bonds is

Options

A. `H_2N-HcdotsNH_3gtHO-HcdotsOH_2gtF-HcdotsF-H`
B. `H_2N-HcdotsNH_3ltHO-HcdotsOH_2ltF-HcdotsF-H`
C. `H_2N-HcdotsNH_3gtF-HcdotsF-HgtHO-HcdotsOH_2`
D. `H_2N-HcdotsNH_3ltHO-HcdotsOH_2gtF-HcdotsF-H`

Answer

To determine the order of strength of hydrogen bonds, we need to consider the electronegativity of the elements involved. Hydrogen bonds occur when hydrogen is covalently bonded to a highly electronegative atom, which creates a partial positive charge on hydrogen and a partial negative charge on the electronegative atom. The strength of hydrogen bonds increases with the electronegativity of the atom bonded to hydrogen.

### Step-by-Step Solution:

1. **Identify the Elements Involved**: The elements typically involved in hydrogen bonding 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 hydrogen bond formed with hydrogen.

3. **Compare Electronegativity Values**:
- Fluorine (F) has the highest electronegativity value (approximately 4.0).
- Oxygen (O) has a lower electronegativity value (approximately 3.5).
- Nitrogen (N) has the lowest electronegativity value among these three (approximately 3.0).

4. **Determine the Order of Strength**:
- Since fluorine is the most electronegative, the hydrogen bond formed with fluorine (as in HF) will be the strongest.
- The hydrogen bond formed with oxygen (as in H2O) will be the next strongest.
- The hydrogen bond formed with nitrogen (as in NH3) will be the weakest.

5. **Final Order of Strength**:
- The order of strength of hydrogen bonds is:
1. Fluorine (HF)
2. Oxygen (H2O)
3. Nitrogen (NH3)

### Conclusion:
The correct order of strength of hydrogen bonds is: **Fluorine > Oxygen > Nitrogen**.