Rubidium and caesium
2 marks · EasyExplain, in terms of atomic structure, why rubidium is more reactive than sodium.
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Rubidium atoms have more electron shells, so their outer electron is further from the nucleus and less strongly attracted. This means it is lost more easily, making rubidium more reactive than sodium.
Must show: Mentions more shells / outer electron further from nucleus, Mentions weaker attraction / easier to lose electron
Also accept: Rubidium's outer electron is further from the nucleus than sodium's, so it is lost more easily and rubidium is more reactive.; More shells in rubidium means weaker attraction to the nucleus, so it loses its outer electron more easily.
Common mistakes: Outer electron is closer to the nucleus.; Sodium has more shells.
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Marking points
M1 · 1 mark · Mentions rubidium has more shells or outer electron is further from nucleus than in sodium.
A1 · 1 mark · Mentions weaker attraction to nucleus or lost more easily, linked to increased reactivity.
Worked solution
Rubidium atoms have more electron shells than sodium, so the outer electron in rubidium is further from the nucleus and less strongly attracted to it. This means the outer electron is lost more easily, so rubidium reacts more readily than sodium.