Atomic number 109 · Transition metal
Meitnerium Mt
Meitnerium is a superheavy element named after Lise Meitner, the physicist who first explained nuclear fission. It was first identified in 1982 at GSI in Germany from a single atom. It is often described as the only element named solely after a real, non-mythological woman.
Key properties
| Atomic number | 109 |
|---|---|
| Atomic weight | [277] (No stable isotope; mass number of a representative isotope in brackets) |
| Category | Transition metal |
| Group | 9 |
| Period | 7 |
| Block | d |
| State (25 °C, 1 atm) | Solid |
| Melting point | — |
| Boiling point | — |
| Density | — |
| Electronegativity (Pauling) | — |
| Atomic radius (van der Waals) | — |
| First ionization energy | — |
| Electron affinity | — |
| Oxidation states | 9, 8, 6, 4, 3, 1 |
| Discovered | 1982 |
Electron configuration
- Condensed
- [Rn]7s2 5f14 6d7
- Full
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f14 6s2 6p6 6d7 7s2
- Electrons per shell
- 2 · 8 · 18 · 32 · 32 · 15 · 2
Orbital diagram
Electron configurations of some superheavy elements (beyond 103) are theoretical predictions.
Position in the table
Discovery
On 29 August 1982 Peter Armbruster and Gottfried Münzenberg's team at GSI in Darmstadt detected one atom of element 109 while bombarding a bismuth-209 target with iron-58 ions. The atom was meitnerium-266, identified by its chain of alpha decays through bohrium and beyond. That a single atom could establish a discovery showed how precise decay-chain analysis had become.
GSI proposed Meitner's name in 1992; IUPAC recommended it in 1994 and adopted it officially in 1997. Meitnerium was actually found two years before hassium, element 108, because predictions at the time suggested element 108 would be too unstable to detect, so GSI tried 109 first.
Origin of the name
The element honours Lise Meitner, the Austrian-born physicist who, with Otto Hahn, discovered element 91, protactinium, and who in 1938, with her nephew Otto Frisch, interpreted the splitting of uranium as nuclear fission. Hahn alone received the Nobel Prize for fission, and the element is widely seen as belated recognition of Meitner's work. The symbol is Mt.
Main uses
- Basic research: It has no uses outside science.
- Predicted chemistry: As a member of group 9 with cobalt, rhodium and iridium, it is expected to be a noble metal resembling iridium, but its isotopes are too short-lived for chemical experiments so far.
Isotopes
There are no stable isotopes. The longest-lived confirmed isotope, meitnerium-278, has a half-life of about 4.5 seconds and was observed in the decay chain of element 117, tennessine. Meitnerium-266, the discovery isotope, lasts a few milliseconds. An unconfirmed meitnerium-282 may live for over a minute.
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
- Meitnerium was discovered from the detection of a single atom.
- Lise Meitner was also a co-discoverer of element 91, protactinium.
- Element 109 was discovered two years before element 108.
Same group (9)
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.