Lithium, sodium, potassium, rubidium, caesium.
Alkali metals more reactive as you go down the group. Outer electron more easily lost because further away from nucleus so larger atomic radius, less energy needed to remove it.
All have one outer electron making them reactive and similar physical properties.
Low melting and boiling point, low density and very soft (can be cut with knife).
Always form ionic compounds because so keen to lose outer electron.
Keen to lose an electron to form 1+ ion with stable electronic structure. More reactive metal, easier to lose electron. Loss of electrons - oxidation.
When alkali metals put into cold water, react vigorously. Move around surface fizzing and producing hydrogen. Reactivity increases further down group. Sodium and potassium melt in the heat of the reaction.
An alkali forms which is hydroxide of metal (happens with all alkali metals)
2Na + 2H2O --> 2NaOH + H2
Alkali metal compounds burn with characteristic colours.
Dip wire loop into hydrochloric acid to clean and moisten it. Put loop into powdered sample of compound to be tested. Place end in blue Bunsen flame. Alkali metal ions will give coloured flames. Colour of metal tells you which metal.