Which of the following bonds has the greatest dipole moment (is the most polar)?

• A. H–Br
• B. H–I
• C. H–Cl
• D. H–F

Answer: (D)

Verified step by step guidance

1. Understand that the dipole moment of a bond depends on two main factors: the difference in electronegativity between the two atoms and the distance between their nuclei (bond length). The greater the electronegativity difference, the more polar the bond tends to be.
2. Recall the electronegativity values of the halogens involved: Fluorine (F) has the highest electronegativity, followed by Chlorine (Cl), Bromine (Br), and Iodine (I). Hydrogen (H) has a lower electronegativity than all these halogens.
3. Calculate or compare the electronegativity differences for each bond: \(\Delta \chi = |\chi_{\text{halogen}} - \chi_{\text{H}}|\). The larger this difference, the greater the bond polarity and dipole moment.
4. Consider the bond length: although bond length affects dipole moment, the effect of electronegativity difference is usually more significant in determining polarity for these bonds. Since F is the smallest atom with the highest electronegativity, the H–F bond has a strong dipole moment.
5. Conclude that among the given options, the H–F bond has the greatest dipole moment because it has the largest electronegativity difference and a relatively short bond length, making it the most polar bond.