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 involving different elements, we can analyze the electronegativity of the atoms involved. The strength of hydrogen bonds is influenced by the electronegativity difference between hydrogen and the atom it is bonded to (such as fluorine, oxygen, or nitrogen).

### Step-by-Step Solution:

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

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

3. **Compare Electronegativity Values**:
- Fluorine (F) has the highest electronegativity (approximately 4.0).
- Oxygen (O) has a lower electronegativity (approximately 3.5).
- Nitrogen (N) has an even lower electronegativity (approximately 3.0).

4. **Assess Hydrogen Bond Strength**:
- The hydrogen bond formed between hydrogen and fluorine (H-F) is the strongest due to the high electronegativity of fluorine.
- The hydrogen bond between hydrogen and oxygen (H-O) is weaker than H-F but stronger than H-N.
- The hydrogen bond between hydrogen and nitrogen (H-N) is the weakest among the three.

5. **Order of Strength**: Based on the analysis, the order of strength of hydrogen bonds is:
- H-F > H-O > H-N

### Final Answer:
The order of strength of hydrogen bonds is: **H-F > H-O > H-N**.