Lighting
Xenon is used because atoms or compounds of this element interact with light in a useful and reproducible way.
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Chemical element · reference page
54Xe
Xenon
Xenon is element 54 (Xe), located in period 5, group 18 and the p block. At room temperature its reference phase is gas. Its electron configuration is [Kr] 4d10 5s2 5p6.
Atomic number54
Standard atomic weight131.293(6)
Group18
Period5
Blockp
Electron configuration[Kr] 4d10 5s2 5p6
Electronic structure
What controls its chemistry
The outer electron shell is filled, which strongly reduces the tendency to gain, lose or share electrons. This is the central reason noble gases are much less reactive than neighbouring groups.
The heavier noble gases are not completely inert: under suitable conditions some form compounds, especially with highly electronegative elements. The group trend is therefore low reactivity, not an absolute prohibition on chemistry.
Chemical forms
Compounds, ions and materials
Xenon is monatomic under ordinary conditions. Noble-gas compounds are unusual, but the heavier members can form compounds under strongly oxidising conditions; xenon chemistry in particular includes well-characterised fluorides and oxides.
Physical behaviour
State and phase changes
The reference phase at room temperature is gas. The listed density is 5.894 g/L. The melting point is 161.4 K (-111.7 °C). The boiling point is 165.1 K (-108.1 °C). Pressure, purity and crystal structure can shift measured physical properties.
Occurrence and applications
Where xenon is found and used
In practice, xenon is encountered in lighting, medical imaging equipment and ion propulsion.
In practice
Examples of real uses
Medical imaging equipment
Xenon is used in imaging agents, detector materials or the high-field magnets and specialised components of imaging systems.
Ion propulsion
Xenon is used as a propellant and is ionised and accelerated electrically to produce efficient thrust in spacecraft.
Periodic position
What its neighbours tell us
Xenon is in period 5 and group 18. In the neighbourhood shown here, iodine is immediately to its left in the same period; krypton is above it and radon below it in the same group. These positions make it possible to compare atomic size, ionisation energy and bonding behaviour with nearby elements.
Reference data
Physical and atomic properties
Classificationnoble gas
Phase at room temperatureGas
Electron shells2 · 8 · 18 · 18 · 8
Density5.894 g/L
Melting point161.4 K (-111.7 °C)
Boiling point165.1 K (-108.1 °C)
Pauling electronegativity2.6
First ionisation energy1 170 kJ/mol
Electron affinity—
Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.
History
Discovery and identification
The discovery of xenon is associated with William Ramsay. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.
Isotopes and atomic weight
How isotope composition changes the numbers
The standard atomic weight is 131.293(6). This value refers to the isotopic composition of natural terrestrial material, not to the mass of one specific atom.
Xenon has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.
Safety
Handling and exposure
The gas is not necessarily chemically toxic, but it can displace oxygen in confined spaces. Ventilation and oxygen monitoring matter in bulk handling.