Meitnerium
Meitnerium is a chemical element with symbol Mt and atomic number 109. It is an extremely radioactive synthetic element (an element not found in nature that can be created in a laboratory). The most stable known isotope, meitnerium-278, has a half-life of 7.6 seconds.
Identity
- Atomic mass
- [278] u
- Category
- Transition metals
- Group
- 9
- Period
- 7
- Block
- d
- Oxidation States
- Limited experimental data
- Phase (25 °C)
- Solid
Electronic Structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d7
- Short configuration
- *[Rn] 5f14 6d7 7s2
- Electrons per shell
- 2, 8, 18, 32, 32, 15, 2
- Electronegativity (Pauling)
- —
- Electron affinity
- —
- 1st ionization energy
- —
Physical properties
- Melting point
- —
- Boiling point
- —
- Density
- 37.4 g/cm³
- Molar heat capacity
- —
Chemical behavior of meitnerium
Meitnerium is a superheavy transactinide with symbol Mt and atomic number 109, located in group 9 below iridium. Its ground-state electron configuration is calculated as [Rn] 5f¹⁴ 6d⁷ 7s². Although no direct experimental chemical test has been possible due to its short half-lives and extremely low production rates, relativistic quantum models predict it behaves as an extremely dense and inert noble metal, with stable oxidation states of +3 and +1, and possibly +6 in fluorinated gaseous halides.
Reactivity
Mt + 3/2 F₂ → MtF₃ (predicted)
Computational chemistry models predict it would form meitnerium trifluoride as a stable trivalent coordination species.
Mt + 3 F₂ → MtF₆ (predicted)
Under energetic fluorination conditions it could form volatile hexafluoride analogous to iridium hexafluoride.
Mt + O₂ → no spontaneous reaction (predicted)
Standard electrode potential calculations anticipate it would be an inert noble metal towards oxygen and aqueous corrosion.
Notable compounds
| Compound | Formula | Use or importance |
|---|---|---|
| Meitnerium trifluoride | MtF₃ | Compound predicted as the most stable trivalent halide in solution phase and solid state |
| Meitnerium hexafluoride | MtF₆ | Theoretical volatile species considered the best candidate for future gas-phase chemistry experiments |
| Potassium tetrachloromeitnerate | K[MtCl₄] | Square-planar anionic complex expected for monovalent or trivalent oxidation state |
Electron shell distribution
View in the atom builderIsotopes
All known meitnerium isotopes are radioactive and produced by artificial nuclear synthesis, with eight nuclides known with masses from 266 to 278. The longest-lived identified isotope is meitnerium-278 (²⁷⁸Mt), with a half-life of approximately 7.6 seconds, decaying by alpha emission to bohrium-274. Other characterized isotopes are meitnerium-270 (²⁷⁰Mt, half-life of 0.7 seconds) and historic meitnerium-266 (²⁶⁶Mt, half-life of 1.7 milliseconds).
Occurrence and production
It is an artificial element with no natural presence on Earth. Its synthesis requires nuclear fusion reactions in heavy accelerators colliding iron-58 ions against bismuth-209 targets ('cold fusion'), or bombarding actinium and berkelium with titanium or chromium ions. Production cross-section is minuscule (barely a few picobarns), achieving detection on average of less than one atom per beam week in state-of-the-art accelerators.
History and origin of the name
It was first synthesized on August 29, 1982 at the Heavy Ion Research Center (GSI) in Darmstadt (Germany) by Peter Armbruster and Gottfried Münzenberg's team. The discoverers proposed naming it 'meitnerium' in honor of the famous Austrian physicist Lise Meitner, co-discoverer of uranium nuclear fission along with Otto Hahn. The proposal was ratified by IUPAC in 1997, making Lise Meitner the only historical woman honored with a chemical element bearing exclusively her surname.
Applications and relevance of meitnerium
Uses of the element
It lacks industrial, commercial or medical applications due to its extreme atomic rarity and rapid decay. Its study is of paramount importance in nuclear physics to map nuclear stability at the frontier of the periodic table.
Uses of its compounds
No macroscopic samples of its compounds have been obtained; its behavior is predicted exclusively through relativistic theoretical models.
Health, safety and environment
Biological role
It has no known biological function and is extremely radiotoxic. It does not exist outside individual-atom experiments.
Safety
It is handled only in specialized laboratories (GSI), in shielded cells. Its alpha decays require strict containment.
Environment
There are no spills: traces are treated as radioactive waste.
Frequently asked questions about Meitnerium
Why does the name meitnerium do justice to a pioneering scientist?
Lise Meitner was the physicist who discovered and theoretically explained the nuclear fission of uranium in 1938. However, because she was a woman of Jewish origin in Nazi Europe, the Nobel Committee awarded the prize solely to her collaborator Otto Hahn, ignoring her contribution. By officially naming element 109 'meitnerium' in 1997, the international scientific community permanently acknowledged her genius in the history of physics.
What do relativistic quantum models predict about meitnerium's most stable oxidation state?
In group 9, cobalt prefers the +2 state and rhodium and iridium prefer +3 and +4. In meitnerium, relativistic effects cause an intense quantum contraction in the 7s orbital and a destabilization of the 6d electrons. Quantum chemistry models predict that meitnerium will preferentially favor the +3 oxidation state in coordinated bonds, although its high reduction potential will make it an extremely noble and difficult-to-oxidize metal.
What did the GSI's alpha decay temporal-spatial correlation technique consist of?
When a single atom crosses the SHIP magnetic separator, it lodges in a micrometric position of a pixelated silicon detector. The computer system notes the exact instant and energy deposited by the collision. Within milliseconds, the detector records in that same pixel the expulsion of an alpha particle with meitnerium's exact energy, followed by bohrium decay. This spatiotemporal coincidence completely eliminates background noise.
How does meitnerium synthesis open the way toward the longed-for nuclear 'island of stability'?
The discovery of meitnerium experimentally confirmed that destructive electrostatic repulsion between more than one hundred protons can be compensated by microscopic nuclear shell quantum effects. Each new transactinide synthesized toward the east of the periodic table adds neutrons to the nuclear network, allowing particle physicists to approach step by step the legendary 'island of stability' centered around elements 114 to 126.
Why are so many attempts needed to produce a meitnerium atom?
Meitnerium is created by colliding atomic nuclei in an accelerator. The fusion giving rise to a new nucleus is extremely improbable, and most collisions do not produce the sought element. Therefore, experiments may need days to register a few atoms. Detectors then identify their radioactive decays, which serve as a fingerprint to confirm which element was formed.
Why hasn't meitnerium's chemistry been studied in depth yet?
Meitnerium is produced atom by atom and its isotopes disintegrate very rapidly. This leaves very little time to transport an atom, make it react with other substances and measure the result. Moreover, the produced quantity is insufficient to form a conventional sample. For now, much of what is known about its chemical behavior comes from theoretical models and its position in the periodic table.
How would meitnerium be if we could have an ingot in our hands?
If it were possible to gather enough stable meitnerium atoms, materials physics models predict that it would be a solid metal with bright silvery appearance, with unsurpassable acid resistance and an enormous density of nearly twenty-eight grams per cubic centimeter, far surpassing osmium and platinum. However, its extreme radioactivity would make it impossible to hold.
Main sources consulted: PubChem, Royal Society of Chemistry, NIST, IUPAC. Last revision: November 2026.