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C4 · Periodic TableAQA GCSE Chemistry · 8462 (Triple)

Group 1 — Alkali Metals

Properties and reactions of Group 1 metals. Trends down the group. Reactions with water and oxygen.

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CognitoGroup 1 alkali metals — properties and reactions
Key facts & methods

Properties and trends in Group 1

  • Group 1 metals: Li, Na, K, Rb, Cs, Fr. All have 1 electron in outer shell.
  • All are very reactive metals — react vigorously with water and oxygen.
  • Low density: lithium, sodium and potassium float on water.
  • Soft — can be cut with a knife. Shiny when freshly cut but quickly tarnish in air.
  • Trend going down Group 1: reactivity INCREASES.
  • Reason: outer electron is further from nucleus → less energy needed to remove it → easier to lose → more reactive.

Reactions of Group 1 metals with water

  • All react vigorously with cold water to produce a metal hydroxide + hydrogen gas.
  • General equation: 2M + 2H₂O → 2MOH + H₂
  • Lithium: fizzes steadily. Dissolves. Lithium hydroxide solution formed.
  • Sodium: fizzes more vigorously, melts into a ball, moves rapidly. Sodium hydroxide formed.
  • Potassium: very vigorous, the hydrogen ignites with a lilac flame. Potassium hydroxide formed.
  • Universal indicator in the water → turns purple/blue (alkaline MOH solution).

Reactions with oxygen and storage

Exam questions — 4 questions · 10 marks · AQA 8462 style
Show all working — the AI marks against the AQA mark scheme. Method marks awarded for correct working even if the final answer is wrong.
1 markGroup 1 trendAQA 8462 style

Why does reactivity increase going down Group 1?

A The atoms get larger so there are more electrons to react with
B The outer electron is further from the nucleus and more shielded, so less energy is needed to remove it
C The atoms become lighter going down the group
D The ionic radius decreases going down the group
3 marksReaction with waterAQA 8462 style

Write a word equation for the reaction of potassium with water. Describe what you would observe during this reaction. (3 marks)

Hint: Word equation: metal + water → metal hydroxide + hydrogen. Observations should describe what you SEE: movement, flame colour, disappearance.
+30 XP
1 markWhy stored in oilAQA 8462 style

Why are Group 1 metals stored under oil?

A To stop them from rusting (forming iron oxide)
B To prevent them reacting with oxygen and water vapour in the air
C To keep them at a constant temperature
D To prevent them from dissolving in each other
3 marksPredict rubidium reactionAQA 8462 style

Rubidium (Rb) is below potassium in Group 1. Predict how rubidium would react with water compared to potassium, and write a word equation for the reaction. (3 marks)

Hint: Use the trend: going down Group 1, reactivity increases. Predict: more vigorous, faster, more likely to ignite. Word equation follows the same pattern as Li/Na/K.
+30 XP

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