Oganesson

properties predicted

Oganesson (Og) is a noble gas with atomic number 118. It has no stable isotope and no characteristic isotopic composition on Earth, so it has no standard atomic weight; its longest-lived isotope has mass number 294. Its electron configuration is predicted to be [Rn] 5f14 6d10 7s2 7p6, which gives it 8 valence electrons.

Oganesson key data

Symbol	Og
Atomic number	118
Mass number (longest-lived isotope)	294
Protons	118
Neutrons (longest-lived isotope, oganesson-294)	176
Electrons (neutral atom)	118
Valence electrons	8
Category	Noble gas
Period	7
Group	18
Block	p-block
Noble gas notation	[Rn] 5f14 6d10 7s2 7p6
Full electron configuration	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f14 6s2 6p6 6d10 7s2 7p6
Electrons per shell	2, 8, 18, 32, 32, 18, 8

Mass number: IUPAC CIAAW radioactive elements, from NUBASE2020.

Properties of oganesson

From PubChem, the US National Institutes of Health. Public domain. Most properties of this element are predicted, because only a few atoms have ever been made.

Predicted oxidation states	+6, +4, +2, +1, 0, −1
Discovered	2006

Oganesson electron configuration

The full electron configuration of oganesson is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f14 6s2 6p6 6d10 7s2 7p6. With the noble-gas core collapsed it is [Rn] 5f14 6d10 7s2 7p6, and the outermost subshell is 7p6.

Bohr model of oganesson (Og): a nucleus and seven shells holding 2, 8, 18, 32, 32, 18 and 8 electrons from the inside out. — Bohr model of oganesson (Og). 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 oganesson (Og), [Rn] 5f14 6d10 7s2 7p6, with the radon 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 oganesson (Og). 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 oganesson 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

one atom = 294 / (6.02214076 × 10²³)
= 4.8820 × 10⁻²² g

Atoms in one gram

atoms per gram = 6.02214076 × 10²³ / 294
= 2.0483 × 10²¹ atoms

Oganesson has no standard atomic weight, because it has neither a stable isotope nor a characteristic isotopic composition on Earth. The figure used above is the mass number of oganesson-294, so treat these as nominal.

Oganesson on the periodic table

Oganesson is in period 7, group 18, in the p-block.

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