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Xe

Xenon

Xenon (Xe) is a noble gas with atomic number 54 and an atomic mass of 131.29. Its electron configuration is [Kr] 4d10 5s2 5p6, which gives it 8 valence electrons.

Xenon key data

Symbol Xe
Atomic number 54
Atomic mass (standard atomic weight) 131.29
Molar mass 131.29 g/mol
Protons 54
Neutrons (most abundant isotope, xenon-132) 78
Electrons (neutral atom) 54
Valence electrons 8
Category Noble gas
Period 5
Group 18
Block p-block
Noble gas notation [Kr] 4d10 5s2 5p6
Full electron configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6
Electrons per shell 2, 8, 18, 18, 8

Atomic mass: IUPAC CIAAW abridged standard atomic weights, 2024. Most abundant isotope: NIST Atomic Weights and Isotopic Compositions.

The values are facts and free to use; this page’s selection and presentation are © 2026 ScienceQuest.

Measured properties of xenon

From PubChem, the US National Institutes of Health. Public domain. PubChem’s periodic table gives no value for the rows not shown.

Melting point 161.36 K (−111.79 °C), 95th of 103 by melting point
Boiling point 165.03 K (−108.12 °C), 85th of 93 by boiling point
Density 0.005887 g/cm³, 87th of 96 by density
State at room temperature Gas
Electronegativity 2.6 (Pauling), 8th of 95 by electronegativity
Van der Waals radius 216 pm, joint 40th of 99 by atomic radius
First ionisation energy 12.13 eV (1170 kJ/mol), 10th of 102 by first ionisation energy
Common oxidation states 0
Discovered 1898

Each rank counts down from the highest value, among the elements PubChem’s table gives one for, and links to that property ranked across the whole table. All of them are collected under periodic trends.

Xenon electron configuration

The full electron configuration of xenon is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6. With the noble-gas core collapsed it is [Kr] 4d10 5s2 5p6, and the outermost subshell is 5p6.

Bohr model of xenon (Xe): a nucleus and five shells holding 2, 8, 18, 18 and 8 electrons from the inside out.
Bohr model of xenon (Xe). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.
Orbital box diagram of xenon (Xe), [Kr] 4d10 5s2 5p6, with the krypton core drawn as one bar: one box per orbital, filled by Hund’s rule, showing every orbital drawn holds a pair of electrons.
Orbital diagram of xenon (Xe). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.

Mass of one xenon atom

A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.

Mass of one atom

  1. one atom = 131.29 / (6.02214076 × 10²³)
  2. = 2.1801 × 10⁻²² g

Atoms in one gram

  1. atoms per gram = 6.02214076 × 10²³ / 131.29
  2. = 4.5869 × 10²¹ atoms

Xenon on the periodic table

Xenon is in period 5, group 18, in the p-block.

The other elements of group 18 are helium, neon, argon, krypton, radon and oganesson.

The rest of period 5

Work with xenon