Potassium

Potassium is a soft, silvery metal that reacts with water so violently that the hydrogen it releases catches fire with a lilac flame. Humphry Davy isolated it in 1807, the first metal ever made using electricity. Its symbol, K, comes from kalium, its Latin name. It is mined as potash, salts left behind by ancient evaporated seas, chiefly in Canada.

Plants and animals need potassium, so most potash becomes fertilizer. In the television's remote, potassium forms potassium hydroxide, the strongly alkaline liquid inside each alkaline battery that lets charge flow between the zinc and the manganese dioxide.