9 letters · 13 points in Scrabble
noun a light soft silver-white metallic element of the alkali metal group; oxidizes rapidly in air and reacts violently with water; is abundant in nature in combined forms occurring in sea water and in car
originCoined by British chemist Humphry Davy in 1807, from potassa (a Latinized form of potash) + -ium.
Etymology from Wiktionary, CC BY-SA 3.0