Group 1 Reactivity Trend

IGCSE Edexcel Chemistry
2.2-2.3 Trends in Group 1 reactivity
Key Concept: Reactivity increases down Group 1 because the outer electron is further from the nucleus and more shielded.

Section A: Ordering Reactivity

1. Put lithium, sodium and potassium in order of increasing reactivity. [1]
2. Describe the trend in reactivity down Group 1. [2]
3. Explain the trend in terms of electron distance and shielding. [3]

Section B: Reactions with Air and Water

4. State two differences between the reactions of lithium and potassium with water. [2]
5. Describe what you might observe when potassium reacts with air compared to lithium. [2]
6. Predict how rubidium would react with water compared to potassium. [2]
7. Which metal would react fastest with water, sodium or caesium? Explain. [2]
8. State one safety precaution when demonstrating alkali metals with water. [1]

Total marks: 15

Mark Scheme

1. Li, Na, K [1]
2. Reactivity increases down Group 1 [2]
3. Outer electron is further from nucleus, more shielding, weaker attraction, easier to lose [3]
4. Potassium reacts more vigorously/ignites; lithium reacts more slowly; potassium melts faster [2]
5. Potassium tarnishes faster or burns more readily than lithium; more vigorous oxidation [2]
6. Rubidium reacts more vigorously/possibly explosive compared to potassium [2]
7. Caesium; lower attraction/greater shielding so fastest [2]
8. Wear goggles/use small pieces/use a safety screen/keep under oil [1]