Bond energy trend in hydrogen halides

Steps:

• Atomic radius increases from Br to I in Group 17.
• Larger iodine atom results in longer H-I bond and weaker overlap of hydrogen 1s and iodine p orbitals.
• Bond dissociation energy decreases down the group due to reduced attraction between nuclei and shared electrons.
• Thus, HBr bond energy exceeds HI bond energy, completing the sentence accurately.

Why A is correct:

• Bond dissociation energy follows the periodic trend where it decreases (HF: 570 kJ/mol > HCl: 431 > HBr: 366 > HI: 299 kJ/mol) due to increasing bond length and poorer orbital overlap.

Why the others are wrong:

• B: Bond length of HBr (141 pm) is shorter than HI (161 pm), so "length less" actually completes correctly, but not the intended answer.
• C: Bond polarity (electronegativity difference) is greater for HBr (0.76) than HI (0.46), so this also completes correctly, but not the intended answer.

Final answer: A