Group 17 — practice question

For this question, Q denotes an atom of chlorine, bromine or iodine. Which explanation correctly accounts for the change in volatility as you go down Group 17?

• AInstantaneous dipole-induced dipole forces between molecules become stronger.
• BPermanent dipole-permanent dipole forces between molecules become stronger.
• CThe bond energy of the Q$_2$ molecules decreases.
• DThe first ionisation energy $\text{Q}(g) \rightarrow \text{Q}^+(g) + e^-$ decreases.