Explaining the trend in the reactivity of the halogens
3 marks · EasyThis question is about why chlorine is more reactive than iodine.
State the charge on the ion formed when a chlorine atom gains an electron.
Describe, using electronic configuration, why a chlorine atom is better at gaining an electron than an iodine atom.
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(a) 1−
(b) Chlorine is smaller so the electron is added closer to the nucleus, where it is more strongly attracted. Iodine's outer shell is further away and less strongly attracted to the nucleus; thus, chlorine is more reactive. · must show Chlorine atom is smaller/has fewer shells, Added electron is closer to the nucleus in chlorine, Stronger attraction in chlorine
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Marking points
B1 (a) · 1 mark · States the charge on the chloride ion is 1−.
M1 (b) · 1 mark · Mentions that chlorine's outer shell is closer/smaller atomic radius.
A1 (b) · 1 mark · Correctly links stronger attraction for the added electron to the nucleus in chlorine.
Worked solution
a) The charge is 1−.
b) Chlorine's outer shell is closer to the nucleus, so the added electron feels a stronger attraction. Iodine's outer shell is further away from the nucleus, so the attraction is weaker.