Berkelium isotopes

According to the periodic table, berkelium has Z = 97. Since the sum of the reactant mass numbers is 241 + 4 = 245 and 2 neutrons are produced, the berkelium isotope must have a mass number of 243. 

Separation and purification Table 10.1 Nuclear properties of berkelium isotopes. 

For basic studies on weighable quantities of californium, the Cf isotope is used. Its alpha half-life of 351 4 years [2,3] makes it suitable for chemical/physical experiments, where weighable quantities of californium are required. The Cf isotope is available as an isotopically pure material from the decay of Bk (beta emitter, half-life of 320 days), the latter being the major berkelium isotope obtained from reactors ( Bk is also formed, but it has a 3.5 h half-life). To obtain Cf free of other californium isotopes, it is first necessary to separate berkelium chemically from the californium produced in a reactor, and then permit the Bk to decay to Cf, which can subsequently be chemically separated from the berkelium. Currently, up to 60 mg per year of Bk are produced in the HFIR at ORNL, which is sufBdent to provide multi-milligram amounts of Cf [4]. The only other known production of Bk, and hence isotopically pure Cf (excluding the use of a mass separator), is in the USSR. The quantity of these materials available in the USSR is believed to be less than that produced by the HFIR. 

Studier, P. R. Fields and J. R. Huizenga Berkelium and Californium Isotopes Produced in Neutron Irradiation of Plutonium. Phys. Rev. 96, 1576 (1954). 

Kriterium eines Liickenelementes erftillt. Bei kritischer Betrachtung der Betastabi-litat der Isotope der Elemente Z > 92, kommt man zu der Erkenntnis, daB diese Moglichkeit bei Element 97, Berkelium, tatsachlich gegeben ist. 

Das Berkelium besitzt also keine betaslabilen Isotope und ist somit ein Liickenelement. 

ISOTOPES There are a total of 23 isotopes of berkelium, none of which are found in nature or are stable. Their half-lives range from 600 nanoseconds for Bk-242 to 1,389 years for Bk-247, which is also the most stable isotope that by alpha decay transmutates into americium-243. 

Berkelium is a metallic element located in group 11 (IB) of the transuranic subseries of the actinide series. Berkelium is located just below the rare-earth metal terbium in the lanthanide series of the periodic table. Therefore, it has many chemical and physical properties similar to terbium ( Tb). Its isotopes are very reactive and are not found in nature. Only small amounts have been artificially produced in particle accelerators and by alpha and beta decay. 

The pure metal of berkelium does not exist in nature and has never been directly artificially produced, although the first isotope of berkelium produced was berkelium-243. It was artificially formed by bombarding americium-241 with the nuclei of helium (alpha particles), as follows " Am+lalpha particle = 2 protons + 2 neutron)—> Bk. (Note Two protons as well as two neutrons are found in the nucleus of helium, and thus the two protons changed the atomic number of americium [ jAm] to berkelium [j Bk].) Today a different process is used to produce berkelium in small amounts, as follows Cm+(5n = neutrons X = gamma rays) —> (becomes) —> Bk + P- = (beta-minus decay). 

Because such small amounts of berkehum have been produced, not many uses for it have been found. One use is as a source for producing the element californium by bombarding isotopes of berkehum with high-energy neutrons in nuclear reactors. Berkelium is also used in some laboratory research. 

Californium is a transuranic element of the actinide series that is homologous with dysprosium (gjDy), just above it in the rare-earth lanthanide series. Cf-245 was the first isotope of californium that was artificially produced. It has a half-life of just 44 minutes. Isotopes of californium are made by subjecting berkelium to high-energy neutrons within nuclear reactors, as follows + (neutrons and A, gamma rays) — °Bk — °Cf + (3- (beta particle... 

Neither californium nor its compounds are found in nature. All of its isotopes are produced artificially in extremely small amounts, and all of them are extremely radioactive. All of its isotopes are produced by the transmutation from other elements such as berkelium and americium. Following is the nuclear reaction that transmutates californium-250 into cahfornium-252 Cf + (neutron and A, gamma rays) — Cf + (neutron and A, gamma rays) —> Cf. 

Einsteinium s most stable isotope, einsteinium-252, with a half-life of472 days, decays into berkelium-248 through alpha decay, and then into californium-252 through beta capture. It can also change into fermium-252 through beta decay. 

Berkelium does not occur in nature. The element was synthesized in 1949 at the Lawrence Berkeley Laboratory in Berkeley, California hy Thompson, Ghiorso and Seahorg (Thompson, S.G., Ghiorso, A. and G. T. Seahorg. 1950. Phys. Rev., 77, 838). It has 12 isotopes. It is the fifth man-made transuranium element. Presently, the element has no commercial apphcation. 

Berkelium accumulates in the skeletal system. The radiation can cause damage to red blood cells. The maximum permissible body burden reported for the isotope Bk-249 in the human skeleton is 0.4 ng (Cunningham, B.B., 1968, Berkelium. In The Encyclopedia of the Chemical Elements. C.A. Hampel, ed., p. 48. New York Reinhold Book Corporation). 

BERKELIUM. [CAS 7440-40-6]. Chemical element, symbol Bk, at. no. 97, at wt. 247 (mass number of the most stable isotope), radioactive metal of the Actinide series, also one of the Transuranium elements. All isotopes of berkelium are radioactive all must be produced synthetically. The element was discovered by G.T. Seaborg and associates at the Metallurgical Laboratory of the University of Chicago in 1949. At that time, the dement was produced by bombarding 241 Am with helium ions. 4i Bk is an alpha-emitter and may be obtained by alpha-bombardment of ,4Cm. 245Cm. or 246Ciu. Ollier nuclides include those of mass numbers 243—246 and 248-250. Probable electronic configuration ... 

The element berkelium was first prepared at the University of California at Berkeley in 1949 by a bombardment of Am. Two neutrons are also produced during the reaction. What isotope of berkelium results from this transmutation Write a balanced nuclear equation. 

Selected nuclear properties of the principal isotopes of berkelium are listed in Table I (6). In addition to these isotopes, ranging from mass numbers 240 to 251, there are spontaneously fissioning isomers known for berkelium mass numbers 242, 243, 244, and 245, all with half-lives of less than 1 /usee. Only 249Bk is available in bulk quantities for chemical studies, as a result of prolonged neutron irradiation of Pu, Am, or Cm (7). About 0.66 g of this isotope has been isolated from... 

There have been no reports of practical applications for any of the isotopes of berkelium. 

The elements with the atomic numbers 97 and 98 (berkelium and californium) at first could not be produced by irradiation with neutrons, because isotopes of Cm exhibiting jfi" transmutation were not known. After milligram amounts of " Am had been produced by reaction (14.14), was obtained in 1949 by Thompson, Ghiorso and others by irradiation with a particles ... 

Plutonium and the four heavier trans-uranium elements whose existence have been reported, americium, curium, berkelium, and californium, were discovered by Professor G. T. Seaborg and his collaborators at the University of California in Berkeley. Americium has been made as the isotope Am by the following reactions ... 

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