Element:	Meitnerium
Symbol:	Mt
Atomic number:	109
Atomic weight:	[268]
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Valence

Origin of name: after Lise Meitner [1878–1968], Austrian–Swedish physicist and mathematician

On August 29, 1992, Element 109 was made and identified by physicists at the Heavy Ion Research Laboratory (G.S.I.), Darmstadt, Germany, by bombarding a target of ²⁰⁹Bi with accelerated nuclei of ⁵⁸Fe. The production of Element 109 has been extremely small. It took a week of target bombardment (10¹¹ nuclear encounters) to produce a single atom of 109. Oganessian and his team at Dubna in 1994 repeated the Darmstadt experiment using a tenfold irradiation dose. One fission event from seven alpha decays of 109 was observed, thus indirectly confirming the existence of isotope ²⁶⁶109. In August 1997, the IUPAC adopted the name meitnerium for this element, honoring L. Meitner.

Four isotopes of meitnerium are now recognized.