CAIE A Level Chemistry 9701 · Group 17
At room temperature, chlorine is a pale green gas, bromine is a dark red-brown liquid and iodine is a grey-black solid. Describe the trend in volatility of these three elements and explain this trend in terms of the forces between the molecules. Describe also the trend in the strength of the covalent bond within the halogen molecules and explain this trend.
6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.