CAIE A Level Chemistry 9701 · Group 17
Chlorine, bromine and iodine are halogens. Their boiling points are –34 °C, 59 °C and 184 °C respectively.
Describe and explain the relative volatility of chlorine and iodine, and explain the relative strength of the bond between the two atoms in a chlorine molecule compared with that in an iodine molecule.
5 marks, so the mark scheme is looking for about 5 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.
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