Which of the following molecules is expected to be the most polar due to differences in electronegativity between its atoms?

• A. HF
• B. HBr
• C. HI
• D. HCl

Answer: (A)

Verified step by step guidance

1. Step 1: Understand that molecular polarity depends on the difference in electronegativity between the atoms involved in the bond. The greater the difference, the more polar the bond is.
2. Step 2: Recall the electronegativity values of the halogens and hydrogen. For example, fluorine (F) has the highest electronegativity among the halogens, followed by chlorine (Cl), bromine (Br), and iodine (I). Hydrogen (H) has a lower electronegativity than all these halogens.
3. Step 3: Calculate or compare the electronegativity differences for each molecule: \(\Delta EN = |EN_{halogen} - EN_H|\). The molecule with the largest \(\Delta EN\) will have the most polar bond.
4. Step 4: Recognize that HF has the largest electronegativity difference because fluorine is the most electronegative element among the options, making the H-F bond highly polar.
5. Step 5: Conclude that among HF, HCl, HBr, and HI, HF is expected to be the most polar molecule due to the greatest difference in electronegativity between hydrogen and fluorine.