C1.2.5 - Group 1 (Alkali Metals)

• What is the electronic structure in group 1?

  1 electron in the outer shell
• How does the electronic structure in group 1 metals relate to its properties?

  Alkali metals are soft, highly reactive with relatively low melting- boiling points. Atomic radius and reactivity increases as we go down group 1, because of 1 additional electron shell with each element, making it easier to lose the electron as its further away from the nucleus making the connection weaker.
• Reactions of group 1 elements with oxygen?

  The group 1 elements react with oxygen from the air to make metal oxides.

  At room temperature, oxygen reacts with the surface of the metal. This forms a white oxide, which covers the surface. The metal below the surface does not react.

  The alkali metals burn vigorously when heated and placed in a gas jar of oxygen. The oxide forms as white smoke.

  For example:

  sodium + oxygen → sodium oxide

  4Na(s) + O2(g) → 2Na2O(s)

  The reactivity of the group 1 elements increases down the group, so their reactions with oxygen get more vigorous.
• Reactions of group 1 metals with chlorine?

  The group 1 elements react vigorously with chlorine. The products of the reactions are chlorides. At room temperature the chlorides are white solids. They dissolve in water to form colourless solutions. For example:

  sodium + chlorine → sodium chloride

  2Na(s) + Cl2(g) → 2NaCl(s)

  The reactions with chlorine get more vigorous going down the group.
• Trend in reactivity in group 1

  When a group 1 element takes part in a reaction, each of its atoms loses its outer electron to form a positively charged ion. The more easily the ions form, the more reactive the metal.

  Going down group 1:

  • the atoms become larger
  • the outer electron becomes further from the nucleus
  • the force of attraction between the nucleus and the outer electron decreases
  • the outer electron is lost more easily
• Reactions of group 1 metals with water?

  The alkali metals react with water to produce a metal hydroxide and hydrogen. For example, sodium reacts with water:

  sodium + water → sodium hydroxide + hydrogen

  2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

  Sodium hydroxide is an alkali. It is a base that dissolves in water to form an alkaline solution. This solution:

  • has a pH greater than 7
  • turns universal indicator solution blue or purple