Oganesson (Og)
Element 118 · Noble gas · Solid at 25 °C · Group 18, Period 7
Oganesson is a synthetic element, produced one atom at a time in particle accelerator experiments. Its isotopes decay within moments, so none of its bulk properties have ever been measured directly — the values chemists cite for it are theoretical predictions. It is named for physicist Yuri Oganessian — only the second element named for a living person.
On the periodic table, oganesson sits in group 18 — the noble gases — in period 7. It is one of 7 elements classified as a noble gas, and at room temperature (25 °C) it is a solid.
The noble gases of group 18 have completely filled outer electron shells, so they have almost no urge to react with anything. All the naturally occurring members are colorless, odorless, monatomic gases at room temperature. Their aloofness is useful in its own right — inert atmospheres, lighting, and cryogenics all rely on it.
Properties of oganesson
| Atomic number (Z) | 118 |
|---|---|
| Symbol | Og |
| Atomic mass | (294) (mass number of the most stable isotope; this element has no standard atomic weight) |
| Category | Noble gas |
| Group | 18 |
| Period | 7 |
| Block | p-block |
| Metal / nonmetal | Nonmetal |
| State at 25 °C | Solid |
| Electron configuration | [Rn] 5f14 6d10 7s2 7p6 |
| Electronegativity (Pauling) | — |
| Melting point | — |
| Boiling point | — |
| Density | — |
Position in the periodic table
Oganesson shares group 18 — the noble gases with Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn). Elements in the same group have the same number of outer electrons, so they tend to behave alike chemically — comparing them is one of the fastest ways to see periodic trends in action.
Physical properties
No melting point, boiling point, or density has been measured for oganesson: too few atoms have ever existed at once. Published figures for these properties are theoretical estimates, so this site shows them as dashes rather than presenting predictions as data.
Data notes
The atomic mass is shown in parentheses because this element has no standard atomic weight; the number given is the mass number of its most stable known isotope.
The state and electron configuration listed for this element are predicted values — it has never been produced in quantities large enough to observe directly.
See also: the interactive periodic table, how to read the periodic table, the element families tour.