Oganesson (Og)
Element 118 · Noble gas · atomic mass [294] u · group 18, period 7
Electron shells: 2, 8, 18, 32, 32, 18, 8
Oganesson completes period 7 and is formally a noble gas, though it is predicted to be a reactive solid rather than an inert gas. Fewer than ten atoms have ever been detected.
Oganesson sits in the noble gas column but is predicted to be a solid that actually reacts.
- Atomic number
- 118
- Atomic mass
- [294] u
- Electron configuration
- [Rn] 7s² 7p⁶ 5f¹⁴ 6d¹⁰
- Group · period · block
- 18 · 7 · p
- Oxidation states
- −1, 0, +1, +2, +4, +6
- Electronegativity
- Not measured
- Melting point
- —
- Boiling point
- —
- Density
- Not measured
- State at 20 °C
- Unknown
- Appearance
- Unknown; presumed solid
- Discovered
- Joint Institute for Nuclear Research and Lawrence Livermore, 2006
118 protons, and 118 electrons when neutral
Mass number of the longest-lived isotope — no standard atomic weight exists
Predicted, not measured
Noble gases
What Oganesson is used for
- Scientific research only
Atomic structure of Oganesson
A neutral oganesson atom has 118 protons and 118 electrons. Its most common isotope carries about 176 neutrons, which is where the mass number 294 comes from. Change the neutron count and you have a different isotope of oganesson; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 32, 32, 18, 8. In orbital notation that is [Rn] 7s² 7p⁶ 5f¹⁴ 6d¹⁰, leaving 8 valence electrons in the outer shell — the ones that do the chemistry.
3D electron orbitals
See where Oganesson's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Oganesson sits in the periodic table
Group 18, with full outer shells and almost no drive to react. Their inertness is exactly what makes them useful for shielding, lighting and cooling.
- Directly above: Radon — same group, so similar chemistry with a smaller atom.
- One proton lighter: Tennessine.
Discovery and naming
Oganesson was discovered by Joint Institute for Nuclear Research and Lawrence Livermore in 2006. Its name comes from Yuri Oganessian.
Every isotope of oganesson is radioactive, so it has no standard atomic weight. Periodic tables show the mass number of its longest-lived isotope in square brackets instead.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Oganesson?
Oganesson has no stable isotope, so it has no standard atomic weight. Periodic tables instead show 294 in square brackets — the mass number of its longest-lived isotope.
How many protons, neutrons and electrons does Oganesson have?
Oganesson has 118 protons, because the atomic number is the proton count and that is what makes an atom Oganesson at all. A neutral Oganesson atom has the same number of electrons, 118. The neutron count varies by isotope; the most common one has about 176, since 294 − 118 = 176.
What is the electron configuration of Oganesson?
The electron configuration of Oganesson is [Rn] 7s² 7p⁶ 5f¹⁴ 6d¹⁰, though for an element this heavy the configuration is predicted from theory rather than measured. Its electrons are arranged 2, 8, 18, 32, 32, 18, 8 across 7 shells.
Is Oganesson a metal?
No. Oganesson is classified as a noble gas, on the right-hand side of the table where elements gain or share electrons rather than losing them.
What group and period is Oganesson in?
Oganesson is in group 18 (the noble gases), period 7, in the p-block. The group is its column and the period is its row.
What is Oganesson used for?
Scientific research only. Oganesson completes period 7 and is formally a noble gas, though it is predicted to be a reactive solid rather than an inert gas.
Who discovered Oganesson, and where does its name come from?
Oganesson (Og) was discovered by Joint Institute for Nuclear Research and Lawrence Livermore in 2006. The name comes from Yuri Oganessian.
Is Oganesson radioactive?
Yes. Every isotope of Oganesson is radioactive — it has no stable form at all, which is why the periodic table shows its mass in square brackets rather than as a standard atomic weight.