Meitnerium
Proposed Name
Atomic Number: 109
Atomic Symbol: Mt
Atomic Weight: 265
Electron Configuration:[Rn]7s^2 5f^14 6d^7History
On August 29, 1982, physicists at the Heavy Ion Research Laboratory, Darmstadt, West
Germany made and identified element 109 by bombing a target of Bi-209 with accelerated nuclei
of Fe-58. If the combined energy of two nuclei is sufficiently high, the repulsive forces between
the nuclei can be overcome.
In this experiment a week of target bombardment was required to produce a single fused
nucleus. The team confirmed the existence of element 109 by four independent measurements.
The newly formed atom recoiled from the target at predicted velocity and was separated from
smaller, faster nuclei by a newly developed velocity filter. The time of flight to the detector and
the striking energy were measured and found to match predicted values.
The nucleus of 266X started to decay 5 ms after striking the detector. A high-energy alpha
particle was emitted, producing 267/107X. This in turn emitted an alpha particle, becoming
258/105Ha, which in turn captured an electron and became 258/104Rf. This in turn decayed into
other nuclides. This experiment demonstrated the feasibility of using fusion techniques as a
method of making new, heavy nuclei.
Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.
Last Updated: 12/19/97, CST Information Services Team
Meitneriumhttp://pearl1.lanl.gov/periodic/elements/109.html [5/10/2001 3:08:57 PM]