Halogen Trends: Volatility and Oxidizing Strength Down Group 17

Steps:

• Recall that volatility of halogens decreases from Cl to I as atomic/molecular size increases, strengthening van der Waals forces and raising boiling points.
• Note that oxidizing strength decreases down the group because larger atomic radius reduces electronegativity, weakening the attraction for electrons to form X⁻ ions.
• Compare trends: both properties decrease from Cl to I, matching option A.
• Eliminate options with mismatched directions (e.g., increasing volatility or oxidizing strength).

Why A is correct:

• Periodic trend in Group 17: atomic size increases down the group, decreasing both volatility (via higher boiling points) and oxidizing power (via lower electronegativity, per the definition of oxidizing agents as electron acceptors).

Why the others are wrong:

• B: Oxidizing strength decreases, not increases, due to reduced electronegativity.
• C: Volatility decreases, not increases, from stronger intermolecular forces.
• D: Both volatility and oxidizing strength decrease, not increase.

Final answer: A