The arrangement of the electrons in an atom
3 marks · NormalThe electronic configuration of element Y is 2,8,2.
Explain the position of element Y in the Periodic Table in terms of its group and period.
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Element Y is in Group 2 and Period 3.
Also accept: Accept explanation that correctly relates outer electrons to group and number of shells to period.
Common mistakes: Mixing up group and period numbers
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Marking points
M1 · 1 mark · Recognises group number = number of electrons in the outer shell.
M1 · 1 mark · Recognises period number = number of electron shells.
A1 · 1 mark · Correctly assigns Y to Group 2 and Period 3.
Worked solution
The electronic configuration 2,8,2 shows that element Y has three electron shells and two electrons in the outer shell.
Therefore, Y is in Period 3 (three shells) and Group 2 (two outer electrons).