There are six alkali metals, Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Caesium (Cs) and Francium (Fr). You've all heard the metal lithium which is inside the batteries. But did you know that you can cut them with a knife? And that they corrode in no-time? Well, the most interesting part comes when they react with water in an exothermic reaction... Just watch the video.