a chemical element with symbol K (from Neo-Latin kalium) and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction and burning with a lilac flame.

The purple tint on these soft potassium cubes is a very thin oxide coating. Exposed to air they turn black in seconds. Exposed to water they would explode, sending off characteristic purple-red flaming drops.