The team at periodicvideos has created a TED-Ed Lesson for every element of the periodic table. This one is about rubidium. Take this lesson to see it dropped in water! Yet another experiment in our "small metallic collider" (aka, the anti-climax machine). We suspect this is the last time you will see it in action.
A curious property of rubidium-silver iodide (RbAg4I5) is that, unlike most alkali metal salts, this solid is highly conducting. Indeed, it has the capacity to conduct electricity like some electrolyte solutions.