The elements in Group I are:
- Francium (radioactive)
For IGCSE you need to be aware of all of these metals, but you only need to know the details about the first three.
All of these metals have to be kept under oil, because they're very reactive, so they can't come into contact with air or water.
Properties of lithium, sodium and potassium:
- Soft metals
- Good conductors of electricity
- Low densities
- Low melting points
- When freshly cut by a knife, they have a shiny surface
- Burn in air, forming white oxides, the white oxides form alkaline solutions of the metal hydroxide when dissolved in water
- React vigorously with water, making an alkaline solution of the metal hydroxide and hydrogen gas
- React vigorously with halogens (e.g. chlorine) forming metal halides (e.g. sodium chloride)
- Potassium reacts the most with water, then sodium and lithium reacts the least with water
Gradual changes (like the one above) are called trends, trends allow chemists to predict things about elements that they have not yet observed.
The further down the group you go, the more reactive the metals are, so obviously francium is the most reactive. For more information on this look at the post on The Periodic Table
When the Group I elements react, they loose an electron, becoming more stable because their electron configuration is now the same as that of a noble gas.