Tantalum isotope

In experiments at the UNILAC accelerator at GSI, Darmstadt, the tantalum isotopes 168 170Ta were transported by the He(KCl) gas-jet and deposited on a polyethylene frit in ARCA II. The dissolution of the collected tantalum activity from the frit was investigated as a function of the a-HiB concentration. Because of the smaller column size in ARCA II (1.6x8 mm) which might cause an earlier breakthrough of the tetravalent and trivalent metal ions it was desirable to decrease the a-HiB concentration. Even with 34 pL of 0.025 M a-HiB, dissolution of >75% of the tantalum activity was achieved in 2 s. The time required for the complete elution of Ta from the column was about 4 s. Similar experiments performed at the Mainz TRIGA reactor with "mNb confirm this result as shown in Figure 14. 

A wide range of experimental techniques has thus been developed to meet the specific requirements of different isotopes, as illustrated in Fig. 3.44 for absorbers under pressure. The soft 7-rays (6.2 keV) of Ta can pass only through thin beryllium windows, however, due to the very narrow natural line width, changes in the isomer shift can be observed very accurately for this tantalum isotope—even in the 500 MPa region—with conventional hydraulic systems. 

What are the atomic number and mass number for each isotope (a) the hydrogen isotope with 2 neutrons (b) the chromium isotope with 28 neutrons (c) the calcium isotope with 22 neutrons (d) the tantalum isotope with 109 neutrons 86. How many neutrons are in an atom with each set of atomic numbers and mass numbers (a) Z = 28,A = 59 (b) Z = 92, A =235 (c) Z = 21,A = 46 (d) Z = 18,A = 42... 

Eighteen isotopes of niobium are known. The metal can be isolated from tantalum, and prepared in several ways. 

Separation of tantalum from niobium requires several complicated steps. Several methods are used to commercially produce the element, including electrolysis of molten potassium fluorotantalate, reduction of potassium fluorotantalate with sodium, or reacting tantalum carbide with tantalum oxide. Twenty five isotopes of tantalum are known to exist. Natural tantalum contains two isotopes. 

Precise measurement of isotope ratios can be obtained by comparing the yields of isotopic ions desorbing from a sample placed on a strongly heated filament that is generally made from platinum, tantalum, rhenium, or tungsten. 

Study of the chemical properties of element 104 has confirmed that it is indeed homologous to hafnium as demanded by its position in the Periodic Table (20). Chemical studies have been made for element 105, showing some similarity to tantalum (25) no chemical studies have been made for elements 106—109. Such studies are very difficult because the longest-Hved isotope of 104 ( 104) has a half-Hfe of only about 1 min, of 105 ( 105) a half-Hfe of about 40 s, of 106 ( 106) a half-Hfe of about 1 s, and of elements 107—109 half-Hves in the range of milliseconds. 

ISOTOPES There are 49 isotopes of tantalum. Only the isotope Ta-181 is stable and accounts for 99.988% of the total mass of the element on Earth. Just 0.012% of the... 

To remove radium and other radioactive constituents from pitchblende, Hahn and Meitner treated pulverized pitchblende repeatedly and for long periods of time with hot concentrated nitric acid. From the insoluble siliceous residue they separated a new radioactive substance, which they called protoactinium. This name has subsequently been shortened to protactinium. When they added a little tantalum salt to a solution containing protactinium, the reactions of the new substance so closely resembled those of tantalum that Hahn and Meitner were unable to separate the two substances (118). Since tantalum is not radioactive, the protactinium could thus be obtained free from other radioelements. Since protactinium is not an isotope of tantalum, it should be possible to separate them from each other (119). By working up large quantities of rich pitchblende residues from the Quinine Works at Braunschweig, Hahn and Meitner were able to extract more active preparations of the new element (49). 

Thus it is evident that there are three natural radioactive isotopes of thallium, seven of lead, four of bismuth, seven elements in the polonium pleiad, three inert radioactive gases, four isotopes of radium, two of actinium, six of thorium, three eka-tantalums, and three uraniums. 

Figure 6.6 Mass spectrum of rare earth elements tREEs) measured by CE-ICP-MS with on line separation of analytes (50 nl solution volume) a) natural isotopic pattern, concentration of each REE - 800ngg b) in an irradiated tantalum target (). S. Becker and H. ]. Dietze, Int. /. Mass Spectrom. Ion Proc. 197, 1-35 (2000). Reproduced by permission of the Royal Society of Chemistry.)...

The group IV B elements titanium, zirconium, and hafnium exhibit the normal isotope effect. Most of the data for the titanium-hydrogen system have been obtained at elevated temperatures. However, extrapolation of the available data (II, 13,31) to room temperature indicates a normal effect for hydrogen and deuterium. The group VB metals vanadium, niobium, and tantalum, on the other hand, exhibit inverse isotope effects indeed, these are the only pure metals that exhibit the inverse effect near room temperature. Extensive data have been reported for these systems. The P-C-T data obtained by Wiswall and Reilly (32) for vanadium hydrogen and deuterium clearly show a greater stability for... 

Ta30, Ta302 etc. These were clear single peaks because there is only one dominant isotope of tantalum. A molybdenum foil was also analyzed and this is shown in Figure 16. Molybdenum has seven dominant isotopes between 92 and 100 and the relative abundances seen in the spectrum is approximately equivalent to the isotope abundances. 

Raw material for the 4 Gd target was produced by spallation reactions in a tantalum metal target by 750-MeV protons at the Isotopes Production Facility at LAMPF. The details of the irradiation and the chemistries associated with separating the hafnium and lanthanide fractions have been reported previously.9 ... 

These observations, along with kinetic isotope effect studies and Hammett correlation studies, support a concerted elimination by a-bond metathesis involving a four-membered transition state (Eq. 2) [23]. A large kinetic isotope effect is observed for the loss of methane from methyl amide complexes lb and lh (Eqs. 3 and 4), comparable to those observed by Buchwald and coworkers for formation of zirconium rj2-thioaldehyde complexes [25] and by Bercaw and coworkers for formation of tantalum rf- imine complexes [5a] through similar transition states. 

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