The Element Potassium The element Potassium was discovered in 1807 by a chemist named Humphry Davy. Potassium was named after the English word “potash”, originally meaning an alkali extracted with water in a pot of burned wood and ashes of plants. Metallic potassium was first isolated by Humphry in 1807 through the electrolysis of molten caustic potash in which potassium was the first isolated metal. The symbol “K” comes from the Latin word meaning kalium and this element is not found in nature as a pure element. Potassium is a chemical element with an atomic number of 19 and an atomic mass of 39. This element has 24 known isotopes from K32-K56 in which k39 is the most stable and there are 3 naturally occurring. Located in Period 4