Explaining the increase in reactivity
2 marks · EasyA sodium atom has 11 electrons. Calculate the number of electrons in its outer shell.
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1 (±0)
Common mistakes: 2; 8; 3
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Marking points
M1 · 1 mark · States/configures shells as 2,8,1 or equivalent working.
A1 · 1 mark · Arrives at 1 electron in the outer shell.
Worked solution
First shell: 2 electrons
Second shell: 8 electrons (total 10)
So outer shell contains 1 electron (11-10=1).