Мейтнерий: Синтезделген радиоактивті элемент

Meitnerium is a synthetic chemical element; it has symbol Mt and atomic number 109. It is an extremely radioactive synthetic element (an element not found in nature, but can be created in a laboratory). The most stable known isotope, meitnerium 278, has a half life of 4.5 seconds, although the unconfirmed meitnerium 282 may have a longer half life of 67 seconds. The GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany, first created this element in 1982. It is named after Lise Meitner. In the periodic table, meitnerium is a d block transactinide element. It is a member of the 7th period and is placed in the group 9 elements, although no chemical experiments have yet been carried out to confirm that it behaves as the heavier homologue to iridium in group 9 as the seventh member of the 6d series of transition metals. Meitnerium is calculated to have properties similar to its lighter homologues, cobalt, rhodium, and iridium.

Superheavy element

Meitnerium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesized in the laboratory, either by fusing two atoms or by observing the decay of heavier elements. Eight different isotopes of meitnerium have been reported with mass numbers 266, 268, 270, and 274–278, two of which, meitnerium 268 and meitnerium 270, have unconfirmed metastable states. A ninth isotope with mass number 282 is unconfirmed. Most of these decay predominantly through alpha decay, although some undergo spontaneous fission.

Meitnerium is the seventh member of the 6d series of transition metals, and should be much like the platinum group metals. The atomic radius of meitnerium is expected to be around 128 pm.

Meitnerium is the first element on the periodic table whose chemistry has not yet been investigated. Unambiguous determination of the chemical characteristics of meitnerium has yet to have been established

The Lawrence Berkeley National Laboratory attempted to synthesize the isotope 271Mt in 2002–2003 for a possible chemical investigation of meitnerium, because it was expected that it might be more stable than nearby isotopes due to having 162 neutrons, a magic number for deformed nuclei; its half life was predicted to be a few seconds, long enough for a chemical investigation. this isotope of meitnerium is currently unknown. In a preliminary step towards determining the chemical properties of meitnerium, the GSI attempted sublimation of the rhodium compounds rhodium(III) oxide (Rh2O3) and rhodium(III) chloride (RhCl3). However, macroscopic amounts of the oxide would not sublimate until 1000 °C and the chloride would not until 780 °C, and then only in the presence of carbon aerosol particles: these temperatures are far too high for such procedures to be used on meitnerium, as most of the current methods used for the investigation of the chemistry of superheavy elements do not work above 500 °C. Following the 2014 successful synthesis of seaborgium hexacarbonyl, Sg(CO)6, studies were conducted with the stable transition metals of groups 7 through 9, suggesting that carbonyl formation could be extended to further probe the chemistries of the early 6d transition metals from rutherfordium to meitnerium inclusive. Nevertheless, the challenges of low half lives and difficult production reactions make meitnerium difficult to access for radiochemists, though the isotopes 278Mt and 276Mt are long lived enough for chemical research and may be produced in the decay chains of 294Ts and 288Mc respectively. 276Mt is likely more suitable, since producing tennessine requires a rare and rather short lived berkelium target. The isotope 270Mt, observed in the decay chain of 278Nh with a half life of 0.69 seconds, may also be sufficiently long lived for chemical investigations, though a direct synthesis route leading to this isotope and more precise measurements of its decay properties would be required.