Electronic configurations and the periodic table
4 marks · NormalComplete the electronic configuration for calcium (atomic number 20).
State the group and period of calcium in the Periodic Table.
Explain what the group and period numbers tell you about calcium’s electron arrangement.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) 2,8,8,2
(b) Group 2, Period 4
(c) The group number tells us calcium has 2 electrons in its outer shell, and the period number tells us it has 4 electron shells.
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Marking points
B1 (a) · 1 mark · Correct electronic configuration given as 2,8,8,2
B2 (b) · 1 mark · Correctly states both group (2) and period (4)
M1 (c) · 1 mark · Identifies group number as number of electrons in outer shell
M2 (c) · 1 mark · Identifies period number as number of electron shells
Worked solution
a) Calcium has atomic number 20. Its configuration is 2 in first shell, 8 in second, 8 in third, 2 in fourth: 2,8,8,2.
b) The number of shells is 4 (period 4), and there are 2 electrons in outer shell (group 2). So: Group 2, Period 4.
c) The group number indicates 2 electrons in outer shell; the period number indicates there are 4 occupied shells.