Drawing diagrams of electronic configurations
2 marks · EasyExplain why the second electron shell fills with up to 8 electrons before the third shell begins to fill.
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Also accept: Energy levels must be fully filled before filling next
Common mistakes: Filling third shell before second is full
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Marking points
B1 · 1 mark · States that inner shells must be filled before electrons go into an outer shell.
B1 · 1 mark · Mentions that the second shell can accommodate a maximum of 8 electrons before the third shell starts to fill.
Worked solution
Electrons fill inner shells first, so the second shell must be complete before electrons are placed in the third shell. The second shell holds up to 8 electrons; only once it is full do electrons enter the third shell.