Xenon (Xe)

Noble gases were believed to be entirely inert until 1962, when Neil Bartlett noticed that platinum hexafluoride oxidised oxygen and reasoned it should manage xenon too; the orange-yellow solid he got that afternoon rewrote a chapter of every chemistry textbook. Xenon ion thrusters have flown on Deep Space 1, Dawn and hundreds of commercial satellites — they produce about the thrust of a sheet of paper resting on your hand, sustained for years. Breathing xenon lowers the voice, the opposite of helium, because it is much denser than air.

Properties

Atomic number

54

Symbol

Xe

Standard atomic weight

131.29 u

Category

Noble gas

Group

18

Period

5

Block

p-block

Electron configuration

[Kr] 5s² 4d¹⁰ 5p⁶

Electrons per shell

2, 8, 18, 18, 8

Melting point

161.36 K — -111.8 °C — -169.2 °F

Boiling point

165.03 K — -108.1 °C — -162.6 °F

Density

0.005887 g/cm³

Electronegativity

2.6 (Pauling)

Oxidation states

0, +2, +4, +6, +8

Discovered

1898 by William Ramsay and Morris Travers

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶

Noble gas shorthand

[Kr] 5s² 4d¹⁰ 5p⁶

Shells

K: 2 · L: 8 · M: 18 · N: 18 · O: 8

What it is used for

• Ion thrusters on satellites and deep-space probes
• Car headlamps and cinema projector lamps
• General anaesthesia, where it is effective but expensive
• Liquid xenon detectors hunting for dark matter and neutrinoless double beta decay
• Xenon flash tubes in cameras and strobes

Density is the gas at 0 °C and 101.325 kPa.

Neighbours in the table

Group 18

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Xenon sits in group 18 with helium, neon, argon, krypton, radon, oganesson.