The Periodic Table
6 marks · NormalThis question is about explaining group trends and the inertness of Group 0 elements using the idea of electronic configuration.
State how the electronic configuration of chlorine is related to its position in the Periodic Table.
Explain why all the elements in Group 1 react similarly when placed in water.
Group 0 (the noble gases) are found at the far right of the Periodic Table.
Explain why the noble gases are so unreactive.
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(a) Chlorine has 7 electrons in its outer shell (group 7), and 3 occupied shells (period 3), so its configuration matches its position (group and period).
(b) Group 1 elements all have 1 electron in their outer shell, so they have similar chemical properties and react in the same way (e.g. with water).
(c) Noble gases have a full outer shell (8 electrons, or 2 for helium), so they have no tendency to lose, gain or share electrons and are therefore unreactive.
Common mistakes: Confusing group number with period number; Saying all noble gases have 8 electrons (He has 2)
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Marking points
E1 (a) · 1 mark · States number of electrons in chlorine's outer shell equals group number (7)
E2 (a) · 1 mark · States number of electron shells equals period number for chlorine (3)
E3 (b) · 1 mark · States Group 1 elements all have 1 electron in their outer shell
E4 (b) · 1 mark · Links same outer shell electrons to similar reactions/properties
E5 (c) · 1 mark · Explains noble gases have a full outer shell (8 or 2 electrons in helium)
E6 (c) · 1 mark · Links full outer shell to lack of tendency to react (no electrons lost/gained/shared)
Worked solution
a. Chlorine’s electronic configuration is 2,8,7. It has 7 electrons in the outer shell, so is found in Group 7. It has 3 shells, so is in Period 3.
b. All Group 1 elements have 1 electron in the outer shell. This similarity gives them similar chemical behavior, such as reacting vigorously with water to produce hydrogen gas and a metal hydroxide.
c. The noble gases have full outer shells (2 electrons for He, 8 for others). This full shell makes them very stable, so they do not need to lose, gain, or share electrons and are therefore unreactive.