|Unbihexium in the periodic table|
|Name, symbol, number||unbihexium, Ubh, 126|
|Group, period, block||n/a, 8, g|
|Standard atomic weight||unknown|
|Electron configuration||[Uuo] 5g2 6f2 7d1 8s2 8p1
2, 8, 18, 32, 34, 20, 9, 3
|Naming||IUPAC systematic element name|
Unbihexium is the temporary name of an undiscovered superheavy chemical element with temporary symbol Ubh and atomic number 126. The element, also known as eka-plutonium or simply element 126, is predicted to be near the centre of the hypothesized island of stability, and thus may have a very long half-life, much greater than what would be predicted without the island of stability. Because of this, it has attracted interest from researchers trying to synthesize it.
A high energy alpha particle was observed and taken as possible evidence for the synthesis of unbihexium. Recent research[which?] suggests that this is highly unlikely as the sensitivity of experiments performed in 1971 would have been several orders of magnitude too low according to current understanding.
Another way to synthesize unbihexium would be to overshoot it by fusion of 130Te and 204Hg; successive alpha decay of the compound nucleus 334
132Utb would land right on 322Ubh (predicted to be relatively stable). 130Te constitutes about 34% of natural tellurium; however, 204Hg only constitutes about 7% of natural mercury. This method of synthesis could also be used to synthesize 298Fl, after the alpha decay of 322Ubh.
It was suggested in 1976 that primordial superheavy elements (mainly livermorium, unbiquadium, unbihexium, and unbiseptium) could be a cause of unexplained radiation damage in minerals. This prompted many researchers to search for it in nature from 1976 to 1983. Some claimed that they had detected alpha particles with the right energies to cause the damage observed, supporting the presence of unbihexium, while some claimed that no unbihexium had been detected. However, the possible extent of primordial unbihexium on Earth is uncertain; it might now only exist in traces, or could even have completely decayed by now after having caused the radiation damage long ago.
Using Mendeleev's nomenclature for unnamed and undiscovered elements, unbihexium should be known as eka-plutonium or dvi-samarium. In 1979 IUPAC published recommendations according to which the element was to be called unbihexium (with the corresponding symbol of Ubh), a systematic element name as a placeholder, until the discovery of the element is confirmed and a name is decided on. The recommendations are largely ignored among scientists, who call it "element 126", with the symbol of (126) or even simply 126.
Nuclear stability and isotopes
The stability of nuclei decreases greatly with the increase in atomic number after plutonium, the heaviest primordial element, so that all isotopes with an atomic number above 101 decay radioactively with a half-life under a day, with an exception of dubnium-268. No elements with atomic numbers above 82 (after lead) have stable isotopes. Nevertheless, because of reasons not very well understood yet, there is a slight increased nuclear stability around atomic numbers 110–114, which leads to the appearance of what is known in nuclear physics as the "island of stability". This concept, proposed by University of California professor Glenn Seaborg, explains why superheavy elements last longer than predicted. Calculations according to the Hartree–Fock–Bogoliubov Method using the non-relativistic Skyrme interaction have proposed Z=126 as a closed proton shell. In this region of the periodic table, N=184 and N=196 have been suggested as closed neutron shells. Therefore the isotopes of most interest are 310Ubh and 322Ubh, for these might be considerably longer-lived than other isotopes. Unbihexium, having a magic number of protons, is predicted to be more stable than other elements in this region, and may have nuclear isomers with very long half-lives.
Atomic and physical
|This section requires expansion. (September 2012)|
Unbihexium is predicted to belong to a new block of valence g-electron atoms, although the g-block's position left of the f-block is speculative. The expected electron configuration is [Uuo] 5g2 6f2 7d1 8s2 8p1, due to the expected smearing out of the energies of 5g, 6f, 7d and 8p orbitals.
Unbihexium is predicted to display a variety of oxidation states, perhaps extending up to +8. Recent calculations have suggested a stable monofluoride UbhF may be possible, resulting from a bonding interaction between the 5g orbital on Ubh and the 2p orbital on fluorine. Other predicted oxidation states include III, IV, VI, and VIII.
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|Extended periodic table (Large version)|