Trends in Halogen Properties Down Group 17

Steps:

• Identify volatility trend: As atomic size increases from Cl to I, van der Waals forces strengthen, raising boiling points and decreasing volatility.
• Identify oxidising agent trend: Larger atomic radius from Cl to I reduces electronegativity, making it harder to gain electrons and weakening oxidising strength.
• Compare to options: Both trends decrease, matching option A.
• Confirm with examples: Cl is more volatile and stronger oxidiser than I.

Why A is correct:

• Halogens' oxidising strength follows the standard reduction potential trend (E° decreases from +1.36 V for Cl₂ to +0.54 V for I₂), confirming decreasing power.

Why the others are wrong:

• B: Oxidising strength decreases, not increases, due to lower electronegativity.
• C: Volatility decreases, not increases, as boiling points rise (Cl₂ -34°C to I₂ 184°C).
• D: Both volatility and oxidising strength decrease, not increase.

Final answer: A