What element has the chemical symbol Kr?

The story behind the answer

Krypton (Kr) is a noble gas, element 36 on the periodic table. Colorless, odorless, and very inert, it was discovered in 1898 by William Ramsay and Morris Travers in the residue of evaporated liquid air. Its name comes from the Greek “kryptos,” meaning “hidden,” reflecting how elusive noble gases are. Krypton is used in photographic flashes, certain fluorescent lamps, and energy-efficient windows.

By contrast, kerosine is a fuel mixture (not an element), “kineticium” isn’t a real element, and curium is element 96 with the symbol Cm, named after Marie and Pierre Curie. Memory tip: KR are the first two letters of KRypton—just don’t mix it up with the fictional “kryptonite.”