Electronic configurations and the periodic table
3 marks · NormalBarium is in Group 2 and Period 6 of the Periodic Table. Explain how you can tell, from its position, the number of electrons in its outer shell and the number of electron shells it has.
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Group 2 means barium has 2 electrons in its outer shell. Period 6 means barium has 6 electron shells.
Also accept: The group tells you the outer electrons, the period tells you the number of shells.
Common mistakes: Mixing up group and period
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Marking points
M1 · 1 mark · States/identifies that group number tells the number of electrons in the outer shell
M2 · 1 mark · States/identifies that period number gives total electron shells
A1 · 1 mark · Applies this: gives correct number for each (2 outer electrons, 6 shells)
Worked solution
Group 2 tells us that barium has 2 electrons in its outer shell.
Period 6 tells us barium has 6 occupied electron shells.