![Krypton element card: symbol Kr, atomic number 36, atomic mass 83.798, electron configuration [Ar] 3d¹⁰ 4s² 4p⁶, oxidation states +2, Noble gas, group 18, period 4, gas at room temperature.](https://stage.chemistry-dictionary.com/wp-content/uploads/2026/09/krypton-chemical-element.webp)
Krypton is a prominent member of group 18 on the far right of the periodic table. Every atom of krypton features a completely full valence electron shell. A valence shell is the outermost layer of electrons in an atom.
This full outer shell makes the gas exceptionally stable and chemically inert under standard conditions. Being inert means it does not easily react or bond with other chemical elements. Companies separate pure krypton from the atmosphere using a process called fractional distillation.
This complex industrial process carefully boils liquefied air to separate out the different gases. Scientists can force krypton to react only under extreme conditions of low temperatures and high electrical energy. They typically react it with highly electronegative elements like pure fluorine gas.
Fluorine pulls electrons strongly enough to form very fragile compounds like krypton difluoride, KrF2. When placed inside a low-pressure electrical discharge tube, krypton behaves uniquely. The applied electricity ionizes the trapped gas and makes it emit a brilliant greenish-white light.
Krypton is much heavier and significantly denser than regular breathable air. It also possesses a remarkably low ability to conduct thermal heat.