Group 1 (I) reactivity

Group 1 metals are very reactive.

  • use tweezers when lifting alkali metals.
  • use a safety screen.
  • wear safety glasses.
  • use small pieces of metal.
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They must be stored under oil to prevent them reacting with the air or water vapour.

All Group 1 elements react with water to produce a metal hydroxide and hydrogen. This is the equation for the reaction between sodium and water:

sodium + water → sodium hydroxide + hydrogen

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

All Group 1 metal reacts with water. There are some common observations and some differences:

  • lithium, sodium and potassium are less dense than water so they float on the surface of the water.
  • the metals move about the surface of the water and fizz as hydrogen gas is produced.
  • they will all release heat as they react as the reactions are exothermic and they will eventually disappear.
  • the solution remaining at the end will be colourless.
  • sodium also melts to form a silvery-grey ball on the surface of the water.
  • potassium will do this as well but it is hard to see as the reaction is so fast and also potassium burns with a lilac flame and crackles as it explodes at the end of the reaction.

Group 1 metals all react in the same way, because each of them loses an electron to form a positive ion with a stable electronic configuration – a full outer shell.

For example, sodium loses one electron to form a sodium ion, Na+, with a full outer shell.

Sodium ionA sodium atom loses one electron to form a sodium ion

Half equation - Higher tier

This can be represented by a half equation:

Na → Na+ + e-

Group 1 elements become more reactive as we move down the group. These atoms are larger because they have more shells. The larger the atom, the further the outer electron is from the nucleus. The force of attraction between the nucleus and the electron is less than for smaller atoms, and the outer electron is lost more easily.

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Most compounds containing Group 1 elements are white and dissolve in water to give colourless solutions.