Nobelium isotopes

Optical spectroscopy is being considered for various nobelium isotopes (Backe et al. 2007). Here, investigations of the relativistic effects of the iimer electrons of nuclei with large Z, which shift the optical levels and ionization potentials are of interest. Relativistic effects are already observed in gold as nomelativistic gold would be white in color. For heavy elements with large... 

The use of larger particles in the cyclotron, for example carbon, nitrogen or oxygen ions, enabled elements of several units of atomic number beyond uranium to be synthesised. Einsteinium and fermium were obtained by this method and separated by ion-exchange. and indeed first identified by the appearance of their concentration peaks on the elution graph at the places expected for atomic numbers 99 and 100. The concentrations available when this was done were measured not in gcm but in atoms cm. The same elements became available in greater quantity when the first hydrogen bomb was exploded, when they were found in the fission products. Element 101, mendelevium, was made by a-particle bombardment of einsteinium, and nobelium (102) by fusion of curium and the carbon-13 isotope. 

In 1957 workers in the United States, Britain, and Sweden announced the discovery of an isotope of element 102 with a 10-minute half-life at 8.5 MeV, as a result of bombarding 244Gm with 13G nuclei. On the basis of this experiment, the name nobelium was assigned and accepted by the Gommission on Atomic Weights of the International Union of Pure and Applied Ghemistry. 

Sixteen isotopes of fermium are known to exist. 257Fm, with a half-life of about 100.5 days, is the longest lived. 250Fm, with a half-life of 30 minutes, has been shown to be a decay product of element 254-102. Chemical identification of 250Fm confirmed the production of element 102 (nobelium). 

The other actinides have been synthesized in the laboratory by nuclear reactions. Their stability decreases rapidly with increasing atomic number. The longest lived isotope of nobelium (102N0) has a half-life of about 3 minutes that is, in 3 minutes half of the sample decomposes. Nobelium and the preceding element, mendelevium (ioiMd), were identified in samples containing one to three atoms of No or Md. 

The name was debated. The priority for the production lay with the Institute for Nuclear Research in Dubna (Russia), under the leadership of G. N. Flerov, where 238U was bombarded with 22Ne. The half-life was about 2.7 seconds. At the University of California, bombardment of curium with carbon gave rise to an isotope with a half-life of 58 minutes. The IUPAC commission suggested the name "lerovium", but nobelium persisted. 

Es entsteht vermutlich das Isotop No 253- Dieses ist ein ot-Strahler ( 3 8,5 MeV) mit einer Halbwertszeit von 10 min (209). Diese ver-ha.ltnisma.Big betrachtliche Halbwertszeit uberrascht zunachst, um so mehr, da die betastabilen Isotope des Nobeliums erwartungsgemaB die Isotope No 258, No 260, No 261, No 262, No 263, No 264 und No 266 sein werden. Somit gehort No 253 zu den Isotopen mit starkem Neu-tronendefizit und es sollte daher ein K-Strahler und kurzlebig sein. 

ISOTOPES There a total of 15 isotopes of nobelium, ranging from 0,25 milliseconds (No-250) to 58 minutes (No-59). None are found in nature all are unstable and are artificially produced In cyclotrons. 

Three groups had roles in the discovery of nobelium. First, scientists at the Nobel Institute of Physics in Stockholm, Sweden, used a cyclotron to bombard Cu-244 with heavy carbon gC-13 (which is natural carbon-12 with one extra neutron). They reported that they produced an isotope of element 102 that had a half-life of 10 minutes. In 1958 the team at Lawrence Laboratory at Berkeley, which included Albert Ghiorso, Glenn Seaborg, John Walton, and Torbjorn Sikkeland, tried to duplicate this experiment and verify the results of the Nobel Institute but with no success. Instead, they used the Berkeley cyclotron to bombard cerium-... 

Although nobelium poses a radiation hazard, the chances of being exposed to it are nil since there is little of it and its isotopes half-lives are only a few seconds and minutes. 

The element was discovered independently by several groups nearly simultaneously. In 1958, Ghiorso, Sikkeland, Walton, and Seaborg at Berkeley, California, synthesized an isotope of this new element by bombardment of a mixture of curium isotopes containing 95% Cm-244 and 4.5% Cm-246 with carbon-12 ions. This new element was named nobelium in honor of Alfred Nobel, discoverer of dynamite. 

The isotope Rf-257 has a half-life of 4.7 sec. It is an alpha-emitter decaying to nobelium-253. The isotopes Rf-258 and Rf-259 have the half-life of 12ms and 3.4 sec., respectively. 

In 1957 a group of scientists at the Argonne Laboratory, the Atomic Energy Research Establishment at Harwell, England, and the Nobel Institute for Physics in Stockholm announced the isolation of element 102 (103). They proposed the name nobelium for this element. However, workers at the University of California Radiation Laboratory could not confirm this claim (104), but did identify the isotope 102254 which they obtained by bombardment of Cm246 with C12 ions in the linear accelerator. They did not immediately propose a name to replace the name nobelium (105). 

In 1973, scientists at Oak Ridge National Laboratory and Lawrence Berkeley Laboratory, produced a relatively long-lived isotope of nobelium through the bombardment of 248C,m with 1 0 ions. A total half-title of 58-5 minutes was computed from the combined data of both laboratories, See also Chemical Elements... 

T. Seaborg at the Lawrence Radiations Laboratory, University of California, was later judged to be the first verified production. The researchers created nobelium by bombarding curium with carbon ions. Only minute quantities of nobelium have been produced, and it is of scientific interest only. The longest lasting isotope has a half-life of three minutes. 

Each of the elements has a number of isotopes (2,4), all radioactive and some of which can be obtained in isotopically pure form. More than 200 in number and mosdy synthetic in origin, they are produced by neutron or charged-particle induced transmutations (2,4). The known radioactive isotopes are distributed among the 15 elements approximately as follows actinium and thorium, 25 each protactinium, 20 uranium, neptunium, plutonium, americium, curium, californium, einsteinium, and fermium, 15 each berkelium, mendelevium, nobelium, and lawrencium, 10 each. There is frequendy a need for values to be assigned for the atomic weights of the actinide elements. Any precise experimental work would require a value for the isotope or isotopic mixture being used, but where there is a purely formal demand for atomic weights, mass numbers that are chosen on the basis of half-life and availability have customarily been used. A list of these is provided in Table 1. 

Nobelium No 102 artificial isotopes only mass number range 250-262... 

The first claim for the discovery of the element nobefium was made in Sweden in 1957. However, neither American nor Soviet researchers could du-phcate the original results, which are now known to have been interpreted incorrectly. The actual discovery of nobelium is credited to researchers in Berkeley, California, who in 1958 bombarded a curium target (95% " Cm and 4.5% Cm) plated on a nickel foil with 60 to 100 MeV ions, and detected both the 8.4 MeV a-particles created by the radioactive decay of No and the °Fm created from the a-decay of No. Known isotopes of nobelium possess 148 to 160 neutrons and 102 protons all are radioactive, with half-fives ranging between 2.5 milliseconds and 58 minutes, and decay by spontaneous fission, a-particle emission, or electron capture. No has the longest half-fife 58 minutes. 

After the discovery of uranium radioactivity by Henri Becquerel in 1896, uranium ores were used primarily as a source of radioactive decay products such as Ra. With the discovery of nuclear fission by Otto Hahn and Fritz Strassman in 1938, uranium became extremely important as a source of nuclear energy. Hahn and Strassman made the experimental discovery Lise Meitner and Otto Frisch provided the theoretical explanation. Enrichment of the spontaneous fissioning isotope U in uranium targets led to the development of the atomic bomb, and subsequently to the production of nuclear-generated electrical power. There are considerable amounts of uranium in nuclear waste throughout the world, see also Actinium Berkelium Einsteinium Fermium Lawrencium Mendelevium Neptunium Nobelium Plutonium Protactinium Rutherfordium Thorium. 

The name nobelium was given to an unconfirmed isotope but has now been adopted for authentic isotopes. 

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