Krypton (from Greek:κρυπτός kryptos "the hidden one") is a chemical element with symbol Kr and atomic number 36. It is a member of group 18 (noble gases) elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquefied air, and is often used with other rare gases in fluorescent lamps.
Three reasons Krypton stands out
1
Used in lasers and lighting, with a faint greenish light.
2
The metre was officially defined by a specific spectral line of this element from 1960 to 1983.
3
It is used in high-speed flash photography to capture images of extremely fast-moving objects.
A noble gas that can still make compounds
Krypton is scarce in air and chemically reserved, but “noble” does not mean absolutely inert. Under demanding conditions it forms compounds, especially with fluorine. Electrically excited krypton produces sharp spectral lines used in specialized lamps, lasers, and the historical definition of the metre.
Recognizing Krypton in Elementle
If Krypton is the mystery element, guesses below atomic number 36 point up and guesses above it point down. Its symbol is Kr: a green letter matches the same position in that symbol, while a yellow letter belongs in another position.
The family clue turns green for noble gas guesses. Compare Argon (Ar), number 18 and Xenon (Xe), number 54: they share the family clue, but their atomic numbers and symbols help you tell them apart.
Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.
The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.