Xenon
Xenon is a heavy noble gas that can form some compounds despite its usually low reactivity.
Xenon brings bright light and unusual chemistry to the noble gases.
Explore Xenon's atom- Atomic number
- 54
- Standard atomic weight
- 131.293(6)
- Family
- Noble gas
- Period
- 5
- Group
- 18
- Standard state
- Gas
In everyday life
Xenon is used in specialised lamps and some spacecraft ion engines.
Something to remember
Despite its noble-gas classification, xenon can form chemical compounds.
Meet its electrons
[Kr] 5s2 4d10 5p6
Published neutral-atom ground-state configuration; excited atoms and ions can differ.
Electrons per shell: 2 · 8 · 18 · 18 · 8.
The playground shows an illustrative shell model. Real electrons are described by quantum orbitals, rather than tiny planets traveling along fixed paths.
A connection to explore
Xenon and krypton are noble gases with some known chemical compounds.
Meet Krypton (Kr)Properties and conditions
- Standard atomic weight
- 131.293(6)CIAAW 2024 standard atomic weight (dimensionless). Parentheses give uncertainty in the last quoted digits. Source flags: g m.CIAAW standard atomic weights ↗ · Retrieved 2026-10-15
- Standard state
- GasPubChem classification, including explicit predictions where stated. Reference temperature and pressure are not supplied in the table.PubChem periodic table ↗ · Retrieved 2026-10-15
- First ionisation energy
- 12.130 eVEnergy to remove the first electron from an isolated neutral gas-phase atom. Uncertainty is not supplied.PubChem periodic table ↗ · Retrieved 2026-10-15
- Electronegativity
- 2.6 Pauling scaleA dimensionless relative measure; values depend on the chosen scale. Uncertainty is not supplied.PubChem periodic table ↗ · Retrieved 2026-10-15
- Melting point
- 161.36 KPubChem reported value. Pressure, allotrope and measurement uncertainty are not specified in the table; consult the cited source.PubChem periodic table ↗ · Retrieved 2026-10-15
- Boiling point
- 165.03 KPubChem reported value. Pressure and measurement uncertainty are not specified in the table; consult the cited source.PubChem periodic table ↗ · Retrieved 2026-10-15
- Density
- 0.005887 g/cm³PubChem reported value. Temperature, pressure, allotrope and measurement uncertainty are not specified in the table; gas densities are especially condition-dependent.PubChem periodic table ↗ · Retrieved 2026-10-15
- Oxidation states
- 0Selected PubChem oxidation states; formal electron bookkeeping, not a list of stable free-ion charges or every possible compound.PubChem periodic table ↗ · Retrieved 2026-10-15
- Discovery
- 1898PubChem discovery attribution. Ancient knowledge and competing priority claims cannot always be represented by a single year.PubChem periodic table ↗ · Retrieved 2026-10-15
- Atomic radius
- 216 pmPubChem tabulated radius. Radius definitions depend on bonding and convention; measurement definition and uncertainty are not supplied in this table.PubChem periodic table ↗ · Retrieved 2026-10-15
- Electron affinity
- Not reportedPubChem reported gas-phase electron affinity. Sign conventions and electronic states matter; uncertainty is not supplied in this table.PubChem periodic table ↗ · Retrieved 2026-10-15
Isotopes, abundance and decay
Isotopes share a proton count but have different neutron counts. This selection includes naturally tabulated compositions and a reference isotope for other elements. It is not a list of every known isotope.
Explore 9 isotopes of Xe
| Isotope | Relative atomic mass | Natural fraction | Half-life | Decay |
|---|---|---|---|---|
| Xe-124 | 123.9058920(19) | 0.000952(3) | No decay observed | ;2β+ ? |
| Xe-126 | 125.9042983(38) | 0.000890(2) | No decay observed | ;2β+ ? |
| Xe-128 | 127.9035310(11) | 0.019102(8) | No decay observed | No decay tabulated |
| Xe-129 | 128.9047808611(60) | 0.264006(82) | No decay observed | No decay tabulated |
| Xe-130 | 129.903509349(10) | 0.040710(13) | No decay observed | No decay tabulated |
| Xe-131 | 130.90508406(24) | 0.212324(30) | No decay observed | No decay tabulated |
| Xe-132 | 131.9041550856(56) | 0.269086(33) | No decay observed | No decay tabulated |
| Xe-134 | 133.90539466(90) | 0.104357(21) | No decay observed | ;2β− ? |
| Xe-136 | 135.907214484(11) | 0.088573(44) | 2.18 Zy (uncertainty 0.05) | ;2β−=100 |
Fractions use NIST’s terrestrial isotopic compositions, which can vary by sample. Parentheses denote uncertainty in the last digits. Half-lives and decay branches use NUBASE2020; # marks estimates, >/< mark limits. “No decay observed” follows that evaluation and does not prove permanent stability. Decay branch intensities are percentages; SF means spontaneous fission, EC electron capture, IT an isomeric transition.
Follow the science
Use these original references to explore the data and context. Atomic weights can vary with isotope composition; values for elements without stable isotopes may describe a representative isotope rather than a standard atomic weight.