Xenon

1 · Identity

Symbol, number

Xe, 54

Oxidation states in water

0 only; a dissolved inert gas with no aqueous chemistry beyond clathrate formation (element entry: fluorides and oxides exist, but XeO₃ and XeO₄ are laboratory oxidants that never occur in water).

Note

The element entry carries everything there is to say; this water chapter is deliberately empty.

Sources

Identity

Name and symbol

Xenon, Xe

Atomic number

54 protons

Position

group 18 · period 5 · p-block · noble gas

CAS number

7440-63-3

Atomic structure

Atomic mass

131.293 u

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶
[Kr] 5s²⁴d¹⁰⁵p⁶

Electrons per shell

2, 8, 18, 18, 8

Valence electrons

8 outer shell

Physical properties

State at room temperature

Gas

Melting point

161.36 K (-111.79 °C)

Boiling point

165.03 K (-108.12 °C)

Density

0.0059 g/cm3 (gas at STP, so 5.887 g/L)

Appearance

colorless gas, exhibiting a blue glow when placed in an electric field

Thermal conductivity

5.65e-3 W/(m·K)

Electrical resistivity

not in sources

Electrical conductivity

not in sources

Crystal structure

face-centered cubic

Molar heat capacity

not in sources

Chemical properties

Oxidation states

0

Electronegativity

2.6 (Pauling Scale)

Ionisation energy

12.13 eV
1st 1,170.4, 2nd 2,046.4, 3rd 3,099.4 kJ/mol

Electron affinity

0 eV

Atomic radius

empirical 140, covalent 140, van der Waals 216 pm

Ionic radius

Xe⁸⁺ 48 pm

Reactivity

A noble gas, very unreactive, yet the first to be shown not fully inert (Bartlett, 1962): its larger, more loosely held outer electrons let it form fluorides, oxides and over a hundred other compounds with the most electronegative elements.

with water

Does not react with water; it dissolves slightly and forms a clathrate hydrate.

with oxygen, air

Does not react with oxygen directly; the oxides are made by hydrolysing the fluorides: $\ce{XeF6 + 3 H2O -> XeO3 + 6 HF}$.

with acids

Does not react with acids.

with halogens

Reacts with fluorine when the gases are irradiated with ultraviolet light or heated, giving the difluoride: $\ce{Xe + F2 -> XeF2}$, the tetrafluoride: $\ce{Xe + 2 F2 -> XeF4}$, and the hexafluoride: $\ce{Xe + 3 F2 -> XeF6}$; no compounds with the other halogens are made directly.

Typical compounds

• XeF₂ xenon difluoride silicon etchant in microprocessor manufacture; fluorinating agent
• XeF₄ xenon tetrafluoride from XeF6 pyrolysis with sodium fluoride
• XeF₆ xenon hexafluoride starting point for most xenon chemistry
• XeO₃ xenon trioxide explosive oxide from hydrolysing the hexafluoride
• XeO₄ xenon tetroxide explodes above -35.9 C into xenon and oxygen

Occurrence, production and use

Crustal abundance

3×10-5 milligrams per kilogram

Oceanic abundance

5×10-5 milligrams per liter

Occurrence and sources

• atmospheric gas, 0.086 ppm by volume air; also gases of some mineral springs
• crustal and oceanic abundance about 0.00003 ppm (BGS figure via RSC); 0.00003 mg/kg crust and 0.00005 mg/L seawater (PubChem)

Extraction, production

Fractional distillation of liquid air

physical separation; no reaction

Uses

Xenon produces a brilliant white flash of light when it is excited electrically and is widely used in strobe lights. The light emitted from xenon lamps is also used to kill bacteria and to power ruby lasers.

Due to its high atomic weight, xenon ions were used as a fuel in an experimental ion engine aboard the space probe Deep Space 1.

Once thought to be completely inert, xenon will form compounds, usually with fluorine, oxygen and platinum. XePtF6, XeF2, XeF4, XeF6 and XeO4 are some of the xenon compounds that have been formed.

The gas is used in making electron tubes, stoboscopic lamps, bactericidal lamps, and lamps used to excite ruby lasers that generate coherent light. Xenon is used in the nuclear energy field in bubble chambers, probes, and other applications where a high molecular weight is of value. The perxenates are used in analytical chemistry as oxidizing agents. 133Xe and 135Xe are produced by neutron irradiation in air cooled nuclear reactors. 133Xe has useful applications as a radioisotope. The element is available in sealed glass containers of gas at standard pressure. Xenon is not toxic, but its compounds are highly toxic because of their strong oxidizing characteristics.

• Lighting and lasers: photographic flash tubes, sunbed lamps, bactericidal lamps for food preparation, ruby-laser pump lamps
• Semiconductors: xenon difluoride etching of silicon
• Pharmaceuticals: xenon difluoride in the manufacture of 5-fluorouracil
• Aerospace: xenon ion propulsion for satellites and spacecraft

Safety, toxicity

GHS classification, signal word Warning

• H280 Contains gas under pressure; may explode if heated Gases under pressure
• H281 Contains refrigerated gas; may cause cryogenic burns or injury Gases under pressure

Discovery and name

Discovered by

William Ramsay

Discovered

1898

First isolated

not in sources

Named by

not in sources

Origin of the name

from the Greek ξένος, meaning 'foreign(er)', 'strange(r)', or 'guest'

Xenon is used in super bright lamps used for deep sea observation.