Atomic number: 55, making it the only element to have taken early retirement
Atomic symbol: Cs (short for 'Christ, have you seen this stuff react with water?!')
Discovered: In 1865 by the German double-act Kirchhoff and Bunsen (this was before the latter hooked up with the long-suffering Beaker)
What does it look like?: A soft, silvery-gold metal
What is it used for?: Atomic clocks and discovering oil - it's frequently used as a drilling aid
What does it do?: Reacts like buggery with water. Seriously, you haven't lived until you've seen a lump of cesium chucked into a glass basin. It's really cool
You might not know this but: Cesium is one of only five metals that's a liquid at room temperature. Whatever you do, please don't drink it