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.
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.
Predict which becomes white more quickly on exposure to air - a piece of rubidium, or a piece of lithium. Explain your answer.
The rubidium becomes white more quickly. This is because rubidium is below lithium in group 1, so rubidium is more reactive.
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.
Write a balanced equation for the reaction of potassium with chlorine.
2K(s) + Cl2(g) → 2KCl(s)
Going down group 1: