Final answer:
The most polar bond among H-F, H-Cl, H-Br, H-I is H-F because fluorine has the highest electronegativity, leading to a larger dipole moment and greater bond polarity.
Step-by-step explanation:
The bond that is most polar among H-F, H-Cl, H-Br, H-I is the H-F bond. This is because the electronegativity difference between hydrogen and fluorine is greater than that between hydrogen and the other halogens (Cl, Br, I). Electronegativity decreases as you move down the halogen group from fluorine to iodine, meaning that fluorine attracts the electrons in the bond the most strongly, creating a greater polarity.
When comparing bonds such as H-F and H-Cl, the electron density is distributed more unevenly in H-F due to fluorine's higher electronegativity, which results in a larger dipole moment, making it the most polar bond of the options provided.