The arrangement of the electrons in an atom
2 marks · EasyThe electronic configuration of an atom is 2,8,5. Explain how you can use this information to work out the group and period of this atom.
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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Group: 5 (because there are 5 electrons in the outermost shell); Period: 3 (because there are 3 shells).
Must show: States group from outer electrons, States period from shell count
Also accept: Outermost shell has 5 electrons: group 5. 3 shells: period 3.
Common mistakes: Confusing group and period; Not linking outer electrons to group
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Marking points
M1 · 1 mark · States group from outer electrons: group 5.
M1 · 1 mark · States period from number of shells: period 3.
Worked solution
There are 3 numbers, so 3 shells, so the atom is in period 3.
The outer shell has 5 electrons, so it is in group 5.