Atomic number 111 · Transition metal
Roentgenium Rg
Roentgenium is a superheavy element named after Wilhelm Röntgen, the discoverer of X-rays. First made at GSI in Germany in 1994, it belongs to group 11 with copper, silver and gold. It is a heavier cousin of gold, yet it exists only as a few atoms that vanish almost as soon as they form.
Key properties
| Atomic number | 111 |
|---|---|
| Atomic weight | [282] (No stable isotope; mass number of a representative isotope in brackets) |
| Category | Transition metal |
| Group | 11 |
| Period | 7 |
| Block | d |
| State (25 °C, 1 atm) | Solid (Predicted) |
| Melting point | — |
| Boiling point | — |
| Density | — |
| Electronegativity (Pauling) | — |
| Atomic radius (van der Waals) | — |
| First ionization energy | — |
| Electron affinity | — |
| Oxidation states | 5, 3, 1, -1 |
| Discovered | 1994 |
Electron configuration
- Condensed
- [Rn]7s2 5f14 6d9
- Full
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f14 6s2 6p6 6d9 7s2
- Electrons per shell
- 2 · 8 · 18 · 32 · 32 · 17 · 2
Orbital diagram
Electron configurations of some superheavy elements (beyond 103) are theoretical predictions.
Position in the table
Discovery
On 8 December 1994 an international team at GSI led by Sigurd Hofmann bombarded a bismuth-209 target with nickel-64 ions and detected three atoms of roentgenium-272, less than a month after the same group had found element 110. Further experiments in 2002 confirmed the result, and in 2003 the joint working group recognised GSI's discovery.
The name proposed by GSI was approved by IUPAC on 1 November 2004, a little over a century after Röntgen's discovery of X-rays in 1895.
Origin of the name
The element honours Wilhelm Conrad Röntgen, the German physicist who discovered X-rays and received the first Nobel Prize in Physics in 1901. His name is often spelled Roentgen in English, hence roentgenium. The symbol is Rg.
Main uses
- Basic research: It has no uses outside science.
- Relativistic effects: Gold's yellow colour is a consequence of relativistic effects on its electrons. In roentgenium these effects are predicted to be stronger still, so it may differ markedly from gold, making it a favourite subject for theoretical chemists.
Isotopes
There are no stable isotopes. The longest-lived confirmed isotope, roentgenium-282, has a half-life of around two minutes and was observed in the decay chain of element 117. An unconfirmed roentgenium-286 may last close to ten minutes. Roentgenium-272, the discovery isotope, lasts a few milliseconds.
In everyday life
It does not exist in nature; only a few atoms at a time are made in accelerators and they decay almost immediately, so it has no connection with daily life or health.
Good to know
- Roentgenium was discovered less than a month after element 110, at the same laboratory.
- The first experiment detected three atoms.
- It sits directly below gold in the periodic table.
Same group (11)
Data sources · Properties: PubChem Periodic Table (US NIH/NLM public data) · Atomic weights: CIAAW 2024 abridged standard atomic weights · Names: Wikidata (CC0); Korean names follow the Korean Chemical Society. Retrieved 2026-09-23.