Berkelium radioactivity

These elements have all been named for famous scientists or for the places of their creation. For example, americium, berkelium, and californium were named after obvious geographical locations. Nobelium was named for the Nobel Institute, although later study proved it was not really created there. Curium was named for Marie Curie, the discoverer of radium. Einsteinium was named for the famous physicist, Albert Einstein. Fermium and lawrencium were named for Enrico Fermi and Ernest O. Lawrence, who made important discoveries in the field of radioactivity. Mendelevium was named for the discoverer of the periodic chart. 

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. 

Continuation of the study of the radioactive elements produced by cyclotron bombardment of lower elements led in 1950 to isolation by tracer techniques of numbers 97 and 98. Bombardment of Am241 with helium ions by S. G. Thompson, A. Ghiorso, and G. T. Seaborg produced 97243 which resembled its analogue, terbium, in its elution from ion-cxchange resins. Since terbium was named from the city of Ytterby, 97 was named from the city in which so many new elements had been discovered, Berkeley, and the name berkelium and symbol Bk have been accepted (89, 90). 

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 ... 

Among the artificial radioactive elements of which Seaborg was discoverer or co-discoverer are Americium, Curium, Berkelium, Californium, and Scaborgium. 

In the period between 1940 and 1961, 11 transuranium elements were discovered by researchers from the University of California at Berkeley (UCB). The term transuranium element refers to elements beyond uranium (atomic numbers greater than 92) in the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. All transuranium elements are unstable or radioactive. Radioactive elements emit energy or particles as they decay into more stable atoms. One of these elements was berkelium. 

All 17 known isotopes of berkelium are radioactive. The most stable is berkelium-247. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element s name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. A radioactive isotope is one that breaks apart and gives off some form of radiation. 

Berkelium-247 has a half life of 1,380 years. The half life of a radioactive element is the time it takes for half of a sample of the element to break down. After 1,380 years, only half of a 10-gram sample (5 grams) of berkelium-247 would be left. The other half would have changed into a different element. After another 1,380 years, half of the remaining berkelium-247 would have changed, leaving 2.5 grams behind. 

The health effects of berkelium have not been studied in detail. Since it is radioactive, scientists assume that it is harmful to human health. 

Gas-phase reactions of the bare monopositive berkelium ion, Bk+, with several reagents including cycloocta-tetraene have been examined by a mass spectrometric technique adapted for the highly radioactive transuranium actinides. The products included 7r-bonded organoberkelium ions such as BkCOT+, presumably, the berkelium-cyclooctatetraenyl half-sandwich complex ion.22... 

Seaborg, Glen T. (1912-1999). An American chemist who won the Nobel Prize for chemistry in 1951 along with McMillan. He did research in nuclear chemistry, physics, and artificial radioactivity. He discovered the elements plutonium, americum, berkelium, californium, einsteinium, fermium, and medelevium with his colleague. He codiscovered numerous isotopes and radioisotopes. His Ph.D. is from the University of California at Berkeley. 

This is the only important oxidation state for Th, and is one of the two for which U is stable in aqueous solution it is moderately stable for Pa and Np also. In water Pu, like Pu, dispropor-tionates into a mixture of oxidation states III, IV, V and VI, while Am not only disproportionates into Am -I- Am 02" " but also (like the strongly oxidizing Cm ) undergoes rapid self-reduction due to its a-radioactivity. As a result, aqueous Am and Cm require stabilization with high concentrations of F ion. Berkelium(IV), though easily reduced, clearly has an enhanced stability, presumably due to its f configuration, and the only other -1-4 ion is Cf, found in the solids CfFq and Cf02. 

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. 

Hum have mass numbers that range from 240 to 251, and are all radioactive. The longest-lived isotope has a mass number of 247 and a half-life of 1,380 years. The ground state electronic configuration of the outer orbitals of berkelium is 5f 6cf7s. In compounds and in aqueous solution, berke-lium is present in oxidation states III (the more stable) and IV. 

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. 

Berkelium. Bk at- wt (most stable known isotope) 247 at. no. 97 valence 3, also 4. A man made radioactive dement second element in the curide series. First produced in 1950 by helium inn bombardment of M,Am yielding... 

When these isotopes become available, chemical studies will be greatly simplified, and the complications introduced by the radioactivity of the actinide elements will be substantially minimized. The longest-lived isotopes of berkelium, californium, and einsteinium are still fairly short-lived substances, and macroscopic amounts have a tremendous associated radioactivity. Nevertheless, it should eventually be possible to prepare and study the solid halides of the actinide elements through the element einsteinium using weighable amounts of reactants. This remains for the future, however. The special experimental problems associated with highly radioactive substances are considered below. 

---