Meitnerium

Meitnerium, ₁₀₉Mt

Meitnerium
Pronunciation	/maɪtˈnɪəriəm/ (myte-NEER-ee-əm) /ˈmaɪtnəriəm/ (MYTE-nər-ee-əm)
Mass number	[278] (unconfirmed: 282)
Meitnerium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Ir ↑ Mt ↓ (Uht) hassium ← meitnerium → darmstadtium
Atomic number (Z)	109
Group	group 9
Period	period 7
Block	d-block
Electron configuration	[Rn] 5f14 6d7 7s2 (predicted)
Electrons per shell	2, 8, 18, 32, 32, 15, 2 (predicted)
Physical properties
Phase at STP	solid (predicted)
Density (near r.t.)	27–28 g/cm3 (predicted)
Atomic properties
Oxidation states	(+1), (+3), (+4), (+6), (+8), (+9) (predicted)
Ionization energies	1st: 800 kJ/mol 2nd: 1820 kJ/mol 3rd: 2900 kJ/mol (more) (all estimated)
Atomic radius	empirical: 128 pm (predicted)
Covalent radius	129 pm (estimated)
Other properties
Natural occurrence	synthetic
Crystal structure	​face-centered cubic (fcc) (predicted)
Magnetic ordering	paramagnetic (predicted)
CAS Number	54038-01-6
History
Naming	after Lise Meitner
Discovery	Gesellschaft für Schwerionenforschung (1982)
Isotopes of meitnerium
Main isotopes Decay abun­dance half-life (t1/2) mode pro­duct 274Mt synth 0.64 s α 270Bh 276Mt synth 0.62 s α 272Bh 278Mt synth 4 s α 274Bh 282Mt synth 67 s? α 278Bh

Meitnerium (Template:PronEng) 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.

Discovery profile

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. The team bombarded a target of bismuth-209 with accelerated nuclei of iron-58 and detected a single atom of the isotope meitnerium-266:

²⁰⁹
₈₃Bi
+ ⁵⁸
₂₆Fe
→ ²⁶⁶
₁₀₉Mt
+
n

Naming

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.

Electronic structure

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	1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s25f146d7

Extrapolated chemical properties of meitnerium

Physical properties

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.

Oxidation states

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.

Chemistry

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.

History of synthesis of isotopes in cold fusion

This section deals with the synthesis of nuclei of meitnerium by so-called "cold" fusion reactions. These are processes which create compound nuclei at low excitation energy (~10-20 MeV, hence "cold"), leading to a higher probability of survival from fission. The excited nucleus then decays to the ground state via the emission of one or two neutrons only.

²⁰⁹Bi(⁵⁸Fe,xn)^267-xMt (x=1)

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. 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.

²⁰⁸Pb(⁵⁹Co,xn)^267-xMt (x=1)

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.

¹⁸¹Ta(⁸⁶Kr,xn)^267-xMt

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.

History of synthesis by hot fusion reactions

²³⁸U(³⁷Cl,xn)^275-xMt

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.

²⁵⁴Es(²²Ne,xn)^276-xMt

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.

Synthesis of isotopes as decay products

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

Chronology of isotope discovery

Isotope	Year discovered	discovery reaction
266Mt	1982	209Bi(58Fe,n)
267Mt	unknown
268Mt	1994	209Bi(64Ni,n)
269Mt	unknown
270Mt	2004	209Bi(70Zn,n)
271Mt	unknown
272Mt	unknown
273Mt	unknown
274Mt	2006	237Np(48Ca,3n)
275Mt	2003	243Am(48Ca,4n)
276Mt	2003	243Am(48Ca,3n)

Chemical yields of isotopes

Cold Fusion

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

Isomerism in meitnerium nuclides

²⁷⁰Mt

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.

²⁶⁸Mt

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.

Future Experiments

The team at RIKEN, Japan, have indicated that as part of their ongoing studies using ²⁴⁸Cm targets, they may study the new reaction ²⁴⁸Cm(²⁷Al,xn) in the future.

External links

• WebElements.com - Meitnerium
• Apsidium - Meitnerium