Potassium 's a chemical element. It's the symbol K (from al-qalyah “plant ashes”, cf. Alkali from the same root), atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash. Elemental potassium's a soft silvery-white metallic alkali metal that oxidizes rapidly in air and's very reactive with water, generating sufficient heat to ignite the evolved hydrogen. Potassium in nature occurs only as ionic salt. As such, it's found dissolved in seawater, and as part… (More on Potassium)