The arrangement of the electrons in an atom
1 mark · EasyWrite the electronic configuration for a calcium atom.
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2,8,8,2
Also accept: 2, 8, 8, 2
Common mistakes: 2,8,10; 2,8,2
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Marking points
B1 · 1 mark · Correctly gives electronic configuration: 2,8,8,2.
Worked solution
Calcium has atomic number 20, so electronic configuration is 2 electrons in the 1st shell, 8 in the 2nd, 8 in the 3rd, and 2 in the 4th: 2,8,8,2.