Boria ( lat. Bohrium , denoted by the symbol Bh, formerly Unnilséptiy , Unnilseptium , Uns , or Eka-rhenium ) is an unstable radioactive chemical element with atomic number 107. Isotopes with mass numbers from 261 to 272 are known. 267 with a half-life of 17 s [1] .
| Bori | |||
|---|---|---|---|
| ← Seaborgy | Khassiy → | |||
| |||
| The appearance of a simple substance | |||
| Probably silvery-white or gray metal | |||
| Atom properties | |||
| Name, symbol, number | Borium / Bohrium (Bh), 107 | ||
| Atomic mass ( molar mass ) | [267] a. e. m. ( g / mol ) | ||
| Electronic configuration | [ Rn ] 5f 14 6d 5 7s 2 | ||
| Atomic radius | presumably 128 pm | ||
| Chemical properties | |||
| Ionization energy (first electron) | presumably 660 kJ / mol ( eV ) | ||
| Thermodynamic properties of a simple substance | |||
| Density (at n. In. ) | presumably 37 g / cm³ | ||
| Melting temperature | Probably above room temperature. | ||
| CAS number | |||
| 107 | Bori |
Bh (270) | |
| 5f 14 6d 5 7s 2 | |
Content
History
The synthesis of the 107th element was first reported in 1976 by a group of Yuri Oganesyan from the Joint Institute for Nuclear Research in Dubna [2] . The technique of this work was to study the spontaneous fission of the products of the reaction of the fusion of bismuth-209 and chromium-54 . Two characteristic half-lives were found: 5 s and 1–2 ms. The first of them was attributed to the decay of the 257 105 core, since the same half-life was also observed for reaction products leading to the formation of the 105th element: 209 Bi + 50 Ti, 208 Pb + 51 V, 205 Tl + 54 Cr. The second half-life was attributed to the nucleus 261 107, which, according to scientists, has two decay modes: spontaneous fission (20%) and α-decay , resulting in a spontaneously fissioning daughter nucleus 257 105 with a half-life of 5 s.
In 1981 , a group of German scientists from the Institute of Heavy Ions ( Ger. Gesellschaft für Schwerionenforschung, GSI ) in Darmstadt investigated the products of the same reaction 209 Bi + 54 Cr, using an improved method to detect the α-decay of nuclides and determine its parameters. In their experiment, scientists from GSI identified 5 events of α-decay of the nucleus 262 107, estimating its lifetime at 4.7 + 2.3–1.6 s [3] .
As further studies of the isotopes of elements 107, 105, and 104 have shown, the nuclei 261 107 and 262 107 are actually born in the 209 Bi + 54 Cr reaction [4] . But many of the conclusions made in 1976 by the JINR group turned out to be erroneous. In particular, the half-life of about 5 s has not 257 105, but 258 105 [5] . With a probability of 1/3, this nuclide experiences beta decay and turns into 258,104 , which very quickly (half-life of 12 ms) divides spontaneously. This means that the products of α-decay of the nucleus 262 107, and not 261 107 [6] were observed at JINR. The lifetime of the isotope 261 107, according to modern estimates, is 12 ms, which is an order of magnitude higher than the result of 1976.
Title
In September 1992, an agreement was reached between scientists from Darmstadt and Dubna that element 107 should be called “nilsbore” in honor of the Danish physicist Niels Bohr [7] , although originally Soviet scientists planned the name “nilsbore” for element 105 (now Dubni ) [ 6] . In 1993, IUPAC recognized the priority of the German group in identifying the 107th element [6] , and in 1994, in its recommendation, proposed the name “borium”, since the names of chemical elements never consisted of the name and surname of the scientist [8] . This proposal was finally approved in 1997 after consulting with Danish chemists [9] .
Known isotopes
| Isotope | Weight | Half-life period [10] | Type of decay |
|---|---|---|---|
| 261 Bh | 261 | 12 +5 −3 ms | α-decay at 257 Db |
| 262 Bh | 262 | 8.0 ± 2.1 ms | α decay of 258 Db |
| 264 Bh | 264 | 0.44 + 0.60 −0.16 sec | α decay at 260 Db |
| 265 Bh | 265 | 0.9 +0.7 −0.3 s | α decay at 261 Db |
| 266 Bh | 266 | 1.7 +8.2 −0.8 s | α decay at 262 Db |
| 267 Bh | 267 | 17 +14 −6 sec | α decay at 263 Db |
| 272 Bh | 272 | 10 +12 −4 sec | α decay at 268 Db |
Notes
- ↑ PA Wilk et al. Evidence for New Isotopes of Element 107: 266 Bh and 267 Bh // Physical Review Letters . - 2000. - Vol. 85 , No. 13 . - p . 2697-2700 .
- ↑ Yu. Ts. Oganessian et al. On spontaneous fission of neutron-deficient isotopes of elements 103, 105 and 107 // Nuclear Physics A. - 1976. - T. 273 , No. 2 . - p . 505-522 .
- ↑ G. Münzenberg et al. Identification of element 107 by α correlation chains // Zeitschrift für Physik A. - 1981. - T. 300 , No. 1 . - pp . 107-108 .
- ↑ G. Münzenberg et al. Element 107 // Zeitschrift für Physik A. - 1989. - T. 333 , No. 2 . - p . 163-175 .
- ↑ FP Heßberger et al. The new isotopes 258 105, 257 105, 254 Lr and 253 Lr // Zeitschrift für Physik A. - 1985. - T. 322 , № 4 . - p . 557-566 .
- ↑ 1 2 3 RC Barber et al. Discovery of the transfermium elements // Pure and Applied Chemistry . - 1993. - Vol. 65 , No. 8 . - p . 1757-1814 .
- ↑ Responses on the Report 'Discovery of the transfermium elements' // Pure and Applied Chemistry . - 1993. - Vol. 65 , No. 8 . - p . 1815-1824 .
- ↑ Commission on Nomenclature of Inorganic Chemistry. Names and symbols of transfermium elements (IUPAC Recommendations 1994) // Pure and Applied Chemistry . - 1994. - Vol. 66 , No. 12 . - p . 2419-2421 .
- ↑ Commission on Nomenclature of Inorganic Chemistry. Names and symbols of transfermium elements (IUPAC Recommendations 1997) // Pure and Applied Chemistry . - 1997. - V. 69 , № 12 . - pp . 2471-2473 .
- ↑ Nudat 2.3