An artificially produced radioactive element with atomic number 109 whose most long-lived isotopes have mass numbers of 266 and 268 with half-lives of 3.4 milliseconds and 70 milliseconds, respectively. Also called unnilennium.
[After Lise MEITNER.]
Dictionary:
meit·ner·i·um (mīt-nûr'ē-əm) ![]() |
An artificially produced radioactive element with atomic number 109 whose most long-lived isotopes have mass numbers of 266 and 268 with half-lives of 3.4 milliseconds and 70 milliseconds, respectively. Also called unnilennium.
[After Lise MEITNER.]
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The seventeenth of the synthetic transuranium elements. Element 109 falls in column 9 of the periodic table under the elements cobalt, rhodium, and iridium. It is expected to have chemical properties similar to those of iridium. See also Iridium; Periodic table; Transuranium elements.
Element 109 was discovered in 1982 by a team under P. Armbruster and G. Münzenberg at the Gesellschaft für Schwerionenforschung (GSI) at Darmstadt, Germany. In a sequence of bombardments of bismuth-209 targets with beams of ions of titanium-50, chromium-54, and iron-58, the compound systems 259105, 263107, and 267109 were produced. The decay analysis of the isotopes produced showed in the case of elements 105 and 107 the production of 258105 and 262107 by reaction channels in which one neutron is emitted. These isotopes have odd neutron and proton numbers and possess a special stability against spontaneous fission. It was shown that alpha-particle decay dominated the decay chains. Spontaneous fission occurs through a 30% electron capture branch of 256105 in 258104. Three decay chains were observed for the three reactions ending by fission of 258104, and the decay of the first atom of element 109 was observed. See also Dubnium;
The single atom of element 109 was produced at a bombarding energy of 299 MeV in the reaction between iron-58 and bismuth-209. A total dose of 7 × 1017 ions was used to bombard thin layers of bismuth during a 250-h irradiation time.
| Columbia Encyclopedia: meitnerium |
In 1982 a German research team led by P. Armbruster and G. Münzenberg at the Institute for Heavy Ion Research at Darmstadt bombarded bismuth-209 atoms with iron-58 ions. On the tenth day of the experiment, one atom was unambiguously identified as an isotope of element 109 with mass number 266 and a half-life of 3.4 msec. The Germans suggested the name meitnerium to honor the Austrian-Swedish physicist and mathematician Lise Meitner. This name was recognized internationally in 1997.
See also synthetic elements; transuranium elements.
| Wikipedia: Meitnerium |
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| Name, Symbol, Number | meitnerium, Mt, 109 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Element category | transition metals | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Group, Period, Block | 9, 7, d | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Appearance | probably light silver green metallic | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Standard atomic weight | [276] g·mol−1 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Electron configuration | perhaps [Rn] 5f14 6d7 7s2 (guess based on iridium) |
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| Electrons per shell | 2, 8, 18, 32, 32, 15, 2 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Phase | presumably a solid | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| CAS registry number | 54038-01-6 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Most-stable isotopes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Meitnerium (pronounced /maɪtˈnɜriəm/ (
listen))[1] is a chemical element in the periodic table that has the symbol Mt and atomic number 109.
Mt is a synthetic element whose most stable known isotope is Mt-276, with a half-life of a 0.7 s.
Meitnerium was first synthesized on August 29, 1982 by a German research team led by Peter Armbruster and Gottfried Münzenberg at the Institute for Heavy Ion Research (Gesellschaft für Schwerionenforschung) in Darmstadt.[2] The team bombarded a target of bismuth-209 with accelerated nuclei of iron-58 and detected a single atom of the isotope meitnerium-266:
Historically, element 109 has been referred to as eka-iridium.
The name meitnerium (Mt) was suggested in honor of the Austrian physicist Lise Meitner. In 1997, the name was officially adopted by the IUPAC.
Meitnerium is element 109 in the Periodic Table. The two forms of the projected electronic structure are:
| Bohr model | 2, 8, 18, 32, 32, 15, 2 |
|---|---|
| Quantum mechanical model[3] | 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s25f146d7 |
Mt should be a very heavy metal with a density around 30 g/cm3 (Co: 8.9, Rh: 12.5, Ir: 22.5) and a high melting point around 2600-2900°C (Co: 1480, Rh: 1966, Ir: 2454). It should be very corrosion resistant more than Ir which is already the most corrosion resistant metal.
Meitnerium is projected to be the sixth member of the 6d series of transition metals and the heaviest member of group 9 in the Periodic Table, below cobalt, rhodium and iridium. This group of transition metals is the first to show lower oxidation states and the +9 state is not known. The latter two members of the group show a maximum oxidation state of +6, whilst the most stable states are +4 and +3 for iridium and +3 for rhodium. Meitnerium is therefore expected to form a stable +3 state but may also portray stable +4 and +6 states.
The +VI state in group 9 is known only for the fluorides which are formed by direct reaction. Therefore, meitnerium should form a hexafluoride, MtF6. This fluoride is expected to be more stable than iridium(VI) fluoride, as the +6 state becomes more stable as the group is descended.
In combination with oxygen, rhodium forms Rh2O3 whilst iridium is oxidised to the +4 state in IrO2. Meitnerium may therefore show a dioxide, MtO2, if eka-iridium reactivity is shown.
The +3 state in group 9 is common in the trihalides (except fluorides) formed by direct reaction with halogens. Meitnerium should therefore form MtCl3, MtBr3 and MtI3 in an analogous manner to iridium.
The first success in this reaction was in 1982 by the GSI team in their discovery experiment with the identification of a single atom of 266Mt in the 1n neutron evaporation channel.[2] The GSI team used the parent-daughter correlation technique. After an initial failure in 1983, in 1985 the team at the FLNR, Dubna, observed alpha decays from the descendant 246Cf indicating the formation of meitnerium. The GSI synthesised a further 2 atoms of 266Mt in 1988 and continued in 1997 with the detection of 12 atoms during the measurement of the 1n excitation function. [4] [5]
This reaction was first studied in 1985 by the team in Dubna. They were able to detect the alpha decay of the descendant 246Cf nuclei indicating the formation of meitnerium atoms. In 2007, in a continuation of their study of the effect of odd-Z projectiles on yields of evaporation residues in cold fusion reactions, the team at LBNL synthesised 266Mt and were able to correlate the decay with known daughters.[6]
There are indications that this cold fusion reaction using a tantalum target was attempted in August 2001 at the GSI. No details can be found suggesting that no atoms of meitnerium were detected.
In 2002-2003, the team at LBNL attempted the above reaction in order to search for the isotope 271Mt with hope that it may be sufficiently stable to allow a first study of the chemical properties of meitnerium. Unfortunately, no atoms were detected and a cross section limit of 1.5 pb was measured for the 4n channel at the projectile energy used. [7]
Attempts to produce long-living isotopes of meitnerium were first performed by Ken Hulet at the Lawrence Livermore National Laboratory (LLNL) in 1988 using the asymmetric hot fusion reaction above. They were unable to detect any product atoms and established a cross section limit of 1 nb.[8]
Isotopes of meitnerium have also been detected in the decay of heavier elements. Observations to date are shown in the table below:
| Evaporation Residue | Observed Mt isotope |
|---|---|
| 288115 | 276Mt |
| 287115 | 275Mt |
| 282113 | 274Mt |
| 278113 | 270Mt |
| 272Rg | 268Mt |
| Isotope | Year discovered | discovery reaction |
|---|---|---|
| 266Mt | 1982 | 209Bi(58Fe,n)[2] |
| 267Mt | unknown | |
| 268Mt | 1994 | 209Bi(64Ni,n)[9] |
| 269Mt | unknown | |
| 270Mt | 2004 | 209Bi(70Zn,n)[10] |
| 271Mt | unknown | |
| 272Mt | unknown | |
| 273Mt | unknown | |
| 274Mt | 2006 | 237Np(48Ca,3n)[10] |
| 275Mt | 2003 | 243Am(48Ca,4n)[11] |
| 276Mt | 2003 | 243Am(48Ca,3n)[11] |
The table below provides cross-sections and excitation energies for cold fusion reactions producing meitnerium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.
| Projectile | Target | CN | 1n | 2n | 3n |
|---|---|---|---|---|---|
| 58Fe | 209Bi | 267Mt | 7.5 pb | ||
| 59Co | 208Pb | 267Mt | 2.6 pb , 14.9 MeV |
Two atoms of 270Mt have been identified in the decay chains of 278113. The two decays have very different lifetimes and decay energies and are also produced from two apparently different isomers in 274Rg. The first isomer decays by emission of an 10.03 MeV alpha particle with a lifetime 7.2 ms. The other decays by emitting an alpha particle with a lifetime of 1.63 s. An assignment to specific levels is not possible with the limited data available. Further research is required.
The alpha decay spectrum for 268Mt appears to be complicated from the results of several experiments. Alpha lines of 10.28,10.22 and 10.10 MeV have been observed. Half-lives of 42 ms, 21 ms and 102 ms have been determined. The long-lived decay is associated with alpha particles of energy 10.10 MeV and must be assigned to an isomeric level. The discrepancy between the other two half-lives has yet to be resolved. An assignment to specific levels is not possible with the data available and further research is required.
| Periodic table | |||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| H | He | ||||||||||||||||||||||||||||||||||||||||
| Li | Be | B | C | N | O | F | Ne | ||||||||||||||||||||||||||||||||||
| Na | Mg | Al | Si | P | S | Cl | Ar | ||||||||||||||||||||||||||||||||||
| K | Ca | Sc | Ti | V | Cr | Mn | Fe | Co | Ni | Cu | Zn | Ga | Ge | As | Se | Br | Kr | ||||||||||||||||||||||||
| Rb | Sr | Y | Zr | Nb | Mo | Tc | Ru | Rh | Pd | Ag | Cd | In | Sn | Sb | Te | I | Xe | ||||||||||||||||||||||||
| Cs | Ba | La | Ce | Pr | Nd | Pm | Sm | Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb | Lu | Hf | Ta | W | Re | Os | Ir | Pt | Au | Hg | Tl | Pb | Bi | Po | At | Rn | ||||||||||
| Fr | Ra | Ac | Th | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Uub | Uut | Uuq | Uup | Uuh | Uus | Uuo | ||||||||||
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This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
| Mt (element) | |
| Hassium (inorganic chemistry) | |
| unnilennium |
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| Where can meitnerium be found in the world? Read answer... | |
| What is the melting point of Meitnerium? Read answer... |
| What is the volume of meitnerium? | |
| Where does the element Meitnerium come from? | |
| What are physical and chemical properties of meitnerium? |
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