Given the binary acids HF, HCl, and HI, which is the strongest acid and why?

• A. All have the same strength because they are in the same group.
• B. HF is the strongest because it has the highest electronegativity.
• C. HI is the strongest because it has the largest atomic radius.
• D. HCl is the strongest because it is in the middle of the group.

Answer: (C)