Xenon

Xenon, ₅₄Xe
	A xenon-filled discharge tube glowing light blue
Xenon
Pronunciation	/ˈzɛnɒn/; (ZEN-on); /ˈziːnɒn/; (ZEE-non);
Appearance	colorless gas, exhibiting a blue glow when placed in an electric field
Standard atomic weight Ar°(Xe)
	131.293±0.006; 131.29±0.01 (abridged);
Xenon in the periodic table
	iodine ← xenon → caesium
Atomic number (Z)	54
Group	group 18 (noble gases)
Period	period 5
Block	p-block
Electron configuration	[Kr] 4d10 5s2 5p6
Electrons per shell	2, 8, 18, 18, 8
Physical properties
Phase at STP	gas
Melting point	161.40 K (−111.75 °C, −169.15 °F)
Boiling point	165.051 K (−108.099 °C, −162.578 °F)
Density (at STP)	5.894 g/L
when liquid (at b.p.)	2.942 g/cm3
Triple point	161.405 K, 81.77 kPa
Critical point	289.733 K, 5.842 MPa
Heat of fusion	2.27 kJ/mol
Heat of vaporization	12.64 kJ/mol
Molar heat capacity	21.01 J/(mol·K)
Atomic properties
Oxidation states	0, +2, +4, +6, +8 (rarely more than 0; a weakly acidic oxide)
Electronegativity	Pauling scale: 2.60
Ionization energies	1st: 1170.4 kJ/mol ; 2nd: 2046.4 kJ/mol ; 3rd: 3099.4 kJ/mol ; ;
Covalent radius	140±9 pm
Van der Waals radius	216 pm
	Spectral lines of xenon
Other properties
Natural occurrence	primordial
Crystal structure	face-centered cubic (fcc)
Thermal conductivity	5.65×10−3 W/(m⋅K)
Magnetic ordering	diamagnetic
Molar magnetic susceptibility	−43.9×10−6 cm3/mol (298 K)
Speed of sound	gas: 178 m·s−1; liquid: 1090 m/s
CAS Number	7440-63-3
History
Discovery and first isolation	William Ramsay and Morris Travers (1898)
Isotopes of xenon

Xenon is a chemical element; it has symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized.

Xenon is used in flash lamps and arc lamps, and as a general anesthetic. The first excimer laser design used a xenon dimer molecule (Xe₂) as the lasing medium, and the earliest laser designs used xenon flash lamps as pumps. Xenon is also used to search for hypothetical weakly interacting massive particles and as a propellant for ion thrusters in spacecraft.

Naturally occurring xenon consists of seven stable isotopes and two long-lived radioactive isotopes. More than 40 unstable xenon isotopes undergo radioactive decay, and the isotope ratios of xenon are an important tool for studying the early history of the Solar System. Radioactive xenon-135 is produced by beta decay from iodine-135 (a product of nuclear fission), and is the most significant (and unwanted) neutron absorber in nuclear reactors.

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