Meitnerium (Mt)

Isotopes of Meitnerium 

Isotope Atomic Mass  Half-life Mode of Decay
Mt-265  266.1366 No data available  No data available 
Mt-266   266.13764 0.0034 seconds α to Bh-262; SF
Mt-267   267.1375 No data available  No data available 
Mt-268   268.1388 0.070 seconds α to Bh-264
Mt-269   269.1391 No data available  No data available 
Mt-270   270.1407 No data available  No data available 
Mt-271   271.1412 No data available  No data available 
Mt-275   275 0.0097 seconds α to Bh-271
Mt-276   276 0.72 seconds α to Bh-272


Meitnerium is a synthetic element (an element not found in nature but that can be created in a laboratory). It was discovered in 1982 by Peter Armbruster, Gottfried Münzenber and their co-workers at Gesellschaft für Schwerionenforschung (GSI — Institute for Heavy Ion Research) in Darmstadt, Germany. Its name originates with Lise Meitner, the Austrian physicist.

Meitnerium is the seventh member of the 6d series of transition metals. Since element 112 (copernicium) has been shown to be a transition metal, it is expected that all the elements from 104 to 112 would form a fourth transition metal series, with meitnerium as part of the platinum group metals. Calculations on its ionization potentials and atomic and ionic radii are similar to those of its lighter homologue iridium, thus implying that meitnerium's basic properties will resemble those of the other group 9 elements: cobalt, rhodium and iridium.

Meitnerium is expected to be a solid under normal conditions and assume a face-centered cubic crystal structure, similarly to its lighter congener, iridium. It should be a very heavy metal with a density of around 37.4 g/cm3, which would be the second-highest of any of the 118 known elements, second only to that predicted for its neighbor hassium (41 g/cm3).

Properties of Meitnerium

Name Meitnerium
Symbol Mt
Atomic number 109
Atomic weight 276
Standard state Presumably a solid at 298 °K
CAS Registry ID 54038-01-6
Group in periodic table 9
Group name None
Period in periodic table 7
Block in periodic table d-block
Color Unknown, but probably metallic and silvery white or grey in appearance
Classification Metallic
Melting point No data available
Boiling point No data available
Density of solid 28.2 g/cm3 (predicted)
Electron configuration [Rn]5f146d77s2 (calculated)
Most stable oxidation states +1, +3, +6 (predicted)

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