Explaining the increase in reactivity
2 marks · NormalState how the electronic configuration changes as you go down Group 1, and explain how this relates to the change in reactivity.
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Atoms down Group 1 have one more electron shell each; the outer electron is further from the nucleus and less strongly attracted, so it is lost more easily making the metal more reactive.
Also accept: Each atom gains an extra electron shell as you go down Group 1, so the outer electron is further from the nucleus and lost more easily.; Going down Group 1, atoms have more shells so the outer electron is less attracted and easier to lose, making reactivity increase.
Common mistakes: Saying ‘more electrons means more reactive’ with no explanation; Not relating to distance/attraction of outer electron
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Marking points
B1 · 1 mark · States as you go down Group 1, atoms have more electron shells/the outer electron is further from the nucleus.
B2 · 1 mark · Explains that this means the outer electron is less strongly attracted (or easier to lose), so reactivity increases.
Worked solution
As you go down Group 1, each atom has one more electron shell, so the outer electron is further from the nucleus.
This means the outer electron is less strongly attracted to the nucleus and is therefore more easily lost, so reactivity increases.