Meitnerium Facts - Mt or Element 109

Meitnerium Element Facts, Properties, and Uses

Meitnerium element tile
Meitnerium or element 109 is a synthetic radioactive metal.

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Meitnerium (Mt) is element 109 on the periodic table. It's one of the few elements that suffered no dispute concerning its discovery or name. Here is a collection of interesting Mt facts, including the element's history, properties, uses, and atomic data.

Interesting Meitnerium Element Facts

  • Meitnerium is a solid, radioactive metal at room temperature. Very little is known about its physical and chemical properties, but based on trends in the periodic table, it is believed to behave as a transition metal, like the other actinide elements. Meitnerium is expected to possess properties similar to its lighter homologous element, iridium. It should also share some common properties with cobalt and rhodium.
  • Meitnerium is a man-made element that does not occur in nature. It was first synthesized by a German research team led by Peter Armbruster and Gottfried Munzenberg in 1982 at the Institute for Heavy Ion Research in Darmstadt. A single atom of the isotope meitnerium-266 was observed from bombardment of a bismuth-209 target with accelerated iron-58 nuclei. Not only did this process create a new element, but it was the first successful demonstration of the use of fusion to synthesize heavy, new atomic nuclei.
  • Placeholder names for the element, before its formal discovery, included eka-iridium and unnilennium (symbol Une). However, most people simply referred to it as "element 109". The only name proposed for the discovered element was "meitnerium" (Mt), in honor of Austrian physicist Lise Meitner, who was one of the discoverers of nuclear fission and the co-discoverer of the element protactinium (together with Otto Hahn). The name was recommended to the IUPAC in 1994 and formally adopted in 1997. Meitnerium and curium are the only elements named for non-mythological women (although Curium is named in honor of both Pierre and Marie Curie).

Meitnerium Atomic Data

Symbol: Mt

Atomic Number: 109

Atomic Mass: [278]

Group: d-block of Group 9 (Transition Metals)

Period: Period 7 (Actinides)

Electron Configuration: [Rn] 5f146d77s2 

Melting Point: unknown

Boiling Point: unknown

Density: The density of Mt metal is calculated to be 37.4 g/cm3 at room temperature. This would give the element the second-highest density of the known elements, after neighboring element hassium, which has a predicted density of 41 g/cm3.

Oxidation States: predicted to be 9. 8. 6. 4. 3. 1 with the +3 state as the most stable in aqueous solution

Magnetic Ordering: predicted to be paramagnetic

Crystal Structure: predicted to be face-centered cubic

Discovered: 1982

Isotopes: There are 15 isotopes of meitnerium, which are all radioactive. Eight isotopes have known half-lives with mass numbers ranging from 266 to 279. The most stable isotope is meitnerium-278, which has a half-life of approximately 8 seconds. Mt-237 decays into bohrium-274 via alpha decay. The heavier isotopes are more stable than the lighter ones. Most meitnerium isotopes undergo alpha decay, although a few undergo spontaneous fission into lighter nuclei. Researchers suspected Mt-271 would be a relatively stable isotope because it would have 162 neutrons (a "magic number"), yet attempts by Lawrence Berkeley Laboratory to synthesize this isotope in 2002-2003 were unsuccessful.

Sources of Meitnerium: Meitnerium may be produced either by fusion two atomic nuclei together or via the decay of heavier elements.

Uses of Meitnerium: Meitnerium's primary use is for scientific research, since only minute amounts of this element have ever been produced. The element plays no biological role and is expected to be toxic due to its inherent radioactivity. Its chemical properties are expected to be similar to noble metals, so if enough of the element is ever produced, it might be relatively safe to handle.


  • Emsley, John (2011). Nature's building blocks: An A-Z Guide to the Elements. Oxford University Press. pp. 492–98. ISBN 978-0-19-960563-7.
  • Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  • Hammond, C. R. (2004). The Elements, in Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN 978-0-8493-0485-9.
  • Rife, Patricia (2003). "Meitnerium." Chemical & Engineering News. 81 (36): 186. doi:10.1021/cen-v081n036.p186
  • Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
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Helmenstine, Anne Marie, Ph.D. "Meitnerium Facts - Mt or Element 109." ThoughtCo, Feb. 16, 2021, Helmenstine, Anne Marie, Ph.D. (2021, February 16). Meitnerium Facts - Mt or Element 109. Retrieved from Helmenstine, Anne Marie, Ph.D. "Meitnerium Facts - Mt or Element 109." ThoughtCo. (accessed June 5, 2023).