Volatility and Intermolecular Forces in Halogens

Steps:

• Volatility measures how easily a substance evaporates, inversely related to boiling point.
• Boiling point rises with stronger intermolecular forces in similar molecules.
• Chlorine (Cl₂) and bromine (Br₂) are nonpolar diatomic gases/liquids with London dispersion forces.
• Dispersion forces strengthen down Group 17 due to increasing atomic size and polarizability, so Br₂ has stronger forces than Cl₂, making Cl₂ more volatile.

Why C is correct:

• C identifies chlorine as more volatile because intermolecular forces are greater in bromine (Br₂) than chlorine (Cl₂), aligning with dispersion force trends that raise Br₂'s boiling point (59°C vs. Cl₂'s -34°C).

Why the others are wrong:

• A: Wrongly names bromine as more volatile despite correctly noting stronger forces in Br₂ (which implies lower volatility for Br₂).
• B: Wrongly names bromine as more volatile and falsely claims stronger forces in Cl₂ than Br₂.
• D: Correctly names chlorine as more volatile but falsely claims stronger forces in Cl₂ than Br₂.

Final answer: C