Group 1 elements

Lithium

  • Reaction with water:
    • Floats
    • Fizzes steadily
    • Becomes smaller and disappears
    • Forms lithium hydroxide and hydrogen
  • Least reactive metal in Group 1
    • Outer shell of electrons is closest to the nucleus so it is difficult to overcome the force of attraction between the protons and electrons
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Sodium

  • Reaction with water:
    • Melts to form a ball
    • Moves around on the surface
    • Fizzes rapidly
    • May burn with an orange flame before disappearing
    • Forms sodium hydroxide and hydrogen
  • More reactive than sodium, less reactive than potassium
    • Outer shell is getting further away from the nucleus so it is easier to lose those electrons
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Potassium

  • Reaction with water:
    • Melts
    • Floats and moves quickly
    • Metal burns with a lilac flame
    • Sometimes a small explosion at the end
    • Forms potassium hydroxide and hydrogen
  • Most reactive of the three elements
    • Outer shell is furthest from the nucleus so are easier to lose
    • (Rubidium, caesium and francium are more reactive still, but these are not covered in IGCSE Chemistry)
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Summary

  • All Group 1 elements react vigorously with water to produce a metal hydroxide and hydrogen
  • All Group 1 elements form ionic compounds- white solids which form colourless alkaline solutions in water
  • Reactivity increases down the group because of the distance of the outer shell from the nucleus- electrons are easier to lose when they are further from the positive nucleus
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