Isotopes of elements

The new elements neptunium and plutonium have been produced in quantity by neutron bombardment of uranium. Subsequently many isotopes have been obtained by transmutation and synthetic isotopes of elements such as Ac and Pa are more easily obtained than the naturally occurring species. Synthetic species of lighter elements, e.g. Tc and Pm are also prepared. 

In 1969 Ghiorso, Nurmia, Harris, K.A.Y. Eskola, and P.E. Eskola of the University of California at Berkeley reported that they had positively identified two, and possibly three, isotopes of Element 104. The group indicated that, after repeated attempts, they produced isotope 260-104 reported by the Dubna groups in 1964. 

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. 

The acceptance of the name was premature because both Russian and American efforts now completely rule out the possibility of any isotope of Element 102 having a half-life of 10 min in the vicinity of 8.5 MeV. Early work in 1957 on the search for this element, in Russia at the Kurchatov Institute, was marred by the assignment of 8.9 +/- 0.4 MeV alpha radiation with a half-life of 2 to 40 sec, which was too indefinite to support discovery claims. 

Ernest O. Lawrence, inventor of the cyclotron) This member of the 5f transition elements (actinide series) was discovered in March 1961 by A. Ghiorso, T. Sikkeland, A.E. Larsh, and R.M. Latimer. A 3-Mg californium target, consisting of a mixture of isotopes of mass number 249, 250, 251, and 252, was bombarded with either lOB or IIB. The electrically charged transmutation nuclei recoiled with an atmosphere of helium and were collected on a thin copper conveyor tape which was then moved to place collected atoms in front of a series of solid-state detectors. The isotope of element 103 produced in this way decayed by emitting an 8.6 MeV alpha particle with a half-life of 8 s. 

Natural radioactive processes in themselves give rise to changes of one element into another. Emission of an alpha particle reduces the atomic number of an element by two units, and emission of a beta particle increases the atomic number by one unit. Thus, for isotopes of elements near... 

The three isotopes of hydrogen are almost indistinguishable for most chemical purposes, but a mass Spectrometer can see them as three different entities of mass 1, 2, and 3 Da. Isotopes of other elements can also be distinguished. Mass spectrometry is important for its ability to separate the isotopes of elements. 

During the operation of nuclear power reactors, which are fuelled with ceramic UO2 fuel rods, the fission of the nuclei leads to die formation of fission products which are isotopes of elements in all of tire Groups of the Periodic Table. The major fission products, present in 1-10% abundance, fall into five groups divided according to the chemical interaction of each product with the fuel ... 

From its position in the periodic table, all isotopes of element 85 would be expected to... 

All isotopes of element 85, astatine, are intensely radioactive with very short half-lives (p. 795). As a consequence weighable amounts of the element or its compounds cannot be prepared and no bulk properties are known. The chemistry of the element must, of necessity, be studied by tracer techniques on extremely dilute solutions, and this introduces the risk of experimental errors and the consequent possibility of erroneous... 

Nine isotopes of element 104 are now known with certainty in the mass range 255-264 and a tenth, is possible. They have half-lives... 

Six isotopes of element 106 are now known (see Table 31.8) of which the most recent has a half-life in the range 10-30 s, encouraging the hope that some chemistry of this fugitive species might someday be revealed. This heaviest isotope was synthsised by the reaction Cm( Ne,4n) 106 and the present uncertainty in the half-life is due to the very few atoms which have so far been observed. Indeed, one of the fascinating aspects of work in this area is the development of philosophical and mathematical techniques to define and deal with the statistics of a small number of random events or even of a single event. 

Note also the production of new isotopes of elements 107 and 109 in this chain. 

For example, the most stable isotope of element 100, fermium, has a half-life of only 4.5 days ... 

Historical That positive rays could be deflected in electric and magnetic fields was shown as early as 1898 by Wien, but it was not until 1912 that what was to become the forerunner of the modem mass spectrometers was built by JJ. Thompson, who became known as the father of mass spectrometry. The existence of two isotopes of neon (m/e 20 and 22) was demonstrated by Thompson with this instrument. The discovery of stable isotopes of elements has been generally considered the... 

C02-0099. Give the atomic S3Tnbols for all the isotopes of elements between Z — 20 and Z — 40 that have exactly 1.25 times as many neutrons as protons. 

Perrier, C., and E. Segre Radioactive isotopes of element 43. Nature... 

MS is based on the production of gas phase ions and on their separation according to their mass-to-charge (m/z) ratios. It was introduced at the end of the nineteenth century and for a long time it was confined to the physical sciences, being used to study elementary particles of matter. Pioneering works by J. J. Thomson, F. W. Aston and A. J. Dempster provided the basis for the determination of the isotopes of elements. In the 1940s, MS... 

The ejection of the a particle (labelled as a helium nucleus in the above equation) from the nucleus of element X results in the transmutation of X into Y, which has an atomic number two less than that of X (i.e., two positions below it in the periodic table). The particular isotope of element Y which is formed is that with an atomic mass of four less than that of the original isotope of X. 

Using mass spectrometry, it is possible to determine the molecular weight of the compound being analyzed. It is also possible to distinguish between isotopes of elements. Thus, 14N and 15N can be separated and quantified using mass spectrometry. 

Cosmogenic Nuclides Isotopes of elements produced by the action of... 

Fallout or bomb-produced nuclides Isotopes of elements produced from nuclear reactors or by detonation of nuclear devices (often radioactive). 

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-... 

In 1994 and 1995 Dr. Darleane Hoffinan of LLNL in Cahfornia and others from Germany used the Separator for Heavy Ion Reaction Products (SHIP) at the GSI laboratory in Darmstadt, Germany, to produce two new isotopes of element 110. 

Following is one example of the nuclear reaction wherein an isotope of element 115 (ununpentium) decays within a few milliseconds into an isotope of element 113 (ununtrium-283), which in turn decays into element 111 (unununium) ... 

Ununpentium is also known as eka-bismuth because it is homologous to the element bismuth located at the bottom of Group 15 (VA). Its melting point, boihng point, and density are unknown as are many of its other properties. Several isotopes of element 115 were produced by the nuclear reaction that bombarded calcium into a target americium, resulting in the fusion of the calcium nuclei with the americium nuclei to form isotopes of element 115 (ununpentium). 

The nuclear reaction involving the bombardment of curium with calcium that directly produced element 116 occurred on December 6, 2000, at the Joint Institute for Nuclear Research in Dubna, Russia, in cooperation with personnel of the Lawrence-Livermore Berkeley Group. This nuclear reaction resulted in the production of a few atoms of the isotope ununhexium-292, which has a half-life of 0.6 milliseconds and emits four neutrons. Uuh-292 is also the most stable isotope of element 116 as it continues to decay into elements with Z numbers of 114, 112, 110, 108, and 106, plus emitting four alpha particles for each transmutation. (Z numbers are the number of protons in the nuclei of atoms.)... 

Since isotopes of element 116 may not have been produced, there are no uses for it. 

Fig. 1.2 Number of stable isotopes of elements with even and odd number of protons (radioactive isotopes with half-lives greater than 10 years are included)...

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