Xenon (Xe)

Xenon (symbol Xe) is the chemical element with atomic number 54: a noble gas, with an atomic mass of 131.29 u. Discovered in 1898 (William Ramsay and Morris Travers).

Xenon is the rarest of the stable noble gases in the atmosphere, at less than one part in ten million. It produces an intense, near-sunlight glow, propels space probes and can even serve as an anesthetic. In 1962, it overturned the dogma that noble gases never react.

Key facts

Atomic number: 54
Symbol: Xe
French name: Xénon
Atomic mass: 131.29 u
Molar mass: 131.29 g/mol
Family: Noble gases
Position: period 5, group 18, p-block
State at 0 °C: Gas
Melting point: -111.7 °C
Boiling point: -108.1 °C
Density: 0.00589 g/cm³
Electronegativity (Pauling): 2.6
First ionization energy: 1,170 kJ/mol
Atomic radius: 108 pm
Electron configuration: [Kr] 4d¹⁰ 5s² 5p⁶
Abundance in Earth's crust: 0.00003 ppm (83rd most abundant element)
Indicative price: 1,800 $/kg (order of magnitude)
Radioactive: no
Discovery: 1898, William Ramsay and Morris Travers

Origin of the name

From the Greek xenos, stranger.

What does xenon look like?

A colorless, odorless gas, about 4.5 times denser than air. Electrically excited, it gives off a bluish-white light.

Where is xenon found?

Air contains about 0.087 ppm (by volume). Traces are also found in some hot springs and meteorites.

Natural sources

Air (traces)

How is xenon produced?

It is extracted from liquid air as a by-product of oxygen production, in very small quantities: a few dozen tonnes a year worldwide, which makes it an expensive gas.

What is xenon used for?

Xenon car headlights and cinema projector lamps.
Ion propulsion for probes and satellites.
General anesthesia (limited by its cost).
Photographic flashes and strobe lights.
Giant detectors hunting for dark matter.

In everyday life

Xenon car headlights
Movie theater projector
Camera flash

Role in living things

No biological role, but it has an anesthetic effect: breathed at high concentration, it puts you to sleep without being metabolized. Some studies also suggest it protects the brain, making it a subject of medical research.

Hazards of xenon

Non-toxic, but it can asphyxiate by displacing oxygen. Being heavy, it collects in the low points of a room.

Cosmic origin

Neutron stars: Created when two neutron stars collide — the “forge” of gold.
Dying stars: Made slowly in red giants (stars like the Sun at the end of their lives).

History of xenon

In 1898, William Ramsay and Morris Travers isolated xenon from the last residues of distilling liquid krypton. They named it after the Greek xenos, “stranger.” In 1962, Briton Neil Bartlett made the first noble gas compound, xenon hexafluoroplatinate.

Did you know?

Inhaling xenon makes your voice deeper, the opposite of helium, because sound travels more slowly in this dense gas.
Experiments such as XENONnT and LZ use several tonnes of liquid xenon to try to catch dark matter particles.
In 2014, the World Anti-Doping Agency banned xenon inhalation, used to boost the body's natural production of EPO.

Isotopes of xenon

Seven stable isotopes and two practically eternal radioactive ones, such as xenon-124: its half-life, first measured in 2019, is nearly a trillion times the age of the Universe.

xenon-124: 0.095% of natural xenon, radioactive, half-life 1.1 × 10²² years. Its double electron capture, the slowest process ever directly observed, was seen in 2019.
xenon-126: 0.089% of natural xenon, stable
xenon-128: 1.91% of natural xenon, stable
xenon-129: 26.401% of natural xenon, stable. Hyperpolarized, it lets MRI see inside the lungs.
xenon-130: 4.071% of natural xenon, stable
xenon-131: 21.232% of natural xenon, stable
xenon-132: 26.909% of natural xenon, stable
xenon-133: radioactive, half-life 5.25 days. Inhaled to study lung ventilation; a telltale sign used to detect nuclear tests.
xenon-134: 10.436% of natural xenon, stable
xenon-135: radioactive, half-life 9.14 h. A powerful neutron “poison” that played a part in the Chernobyl accident.
xenon-136: 8.857% of natural xenon, radioactive, half-life 2.17 × 10²¹ years. Tonnes of xenon-136 are used to search for neutrinoless double beta decay.

Related elements

Same family (noble gases): Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Radon (Rn).

Same column (group 18): Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Radon (Rn), Oganesson (Og).