Lithium
sodium
potassium
rubidium
caesium
francium
they are all alkaline metals they all react with water
lithium is in your watch battery it reacts with air in the cell to produce the cell voltage.
sodium is used in discharge lights mainly street lights (orange glow)
potassium is used to reduce blood pressure in medicines
rubidium
caesium
francium these are radio active and are used by the nuclear industry to produce electricity