Kr

Krypton (from Ancient Greek: κρυπτός, romanized: kryptos "the hidden one") is a chemical element with the symbol Kr and atomic number 36. It is a colorless, odorless, tasteless noble gas that occurs in trace amounts in the atmosphere and is often used with other rare gases in fluorescent lamps. With rare exceptions, krypton is chemically inert. https://en.wikipedia.org/wiki/Krypton