Elements, 2, 5-7 actinide series transuranic

Albert Einstein) Einsteinium, the seventh transuranic element of the actinide series to be discovered, was identified by Ghiorso and co-workers at Berkeley in December 1952 in debris from the first large thermonuclear explosion, which took place in the Pacific in November, 1952. The 20-day 253Es isotope was produced. 

Krebs, Robert E. The history and use of our earth s chemical elements a reference guide. Westport (CT) Greenwood P, 1998. ix, 346p. ISBN 0-313-30123-9 A short history of chemistry — Atomic structure The periodic table of the chemical elements — Alkali metals and alkali earth metals - Transition elements metals to nonmetals — Metallics and metalloids - Metalloids and nonmetals — Halogens and noble gases - Lanthanide series (rare-earth elements) — Actinide, transuranic, and transactinide series... 

The transuranic elements are a subseries within the actinide series with atomic numbers higher than uranium They include the actinides neptunium (53NP) up to... 

Actinide Series (Period 7) ctnd Transuranic Elements... 

As mentioned, a subset of the actinide series is referred to as the transuranic elements, which are the heavy elements with atomic numbers greater than uranium (gjU). This actinide... 

Curium is a synthetic (not natural) transuranic element of the actinide series. It was determined that curiums major valence and oxidation state was +3, similar to other elements of this series. The most stable isotope of curium is curium-247, with a half-life of 1.56xl0 years. 

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. 

Californium is a synthetic radioactive transuranic element of the actinide series. The pure metal form is not found in nature and has not been artificially produced in particle accelerators. However, a few compounds consisting of cahfornium and nonmetals have been formed by nuclear reactions. The most important isotope of cahfornium is Cf-252, which fissions spontaneously while emitting free neutrons. This makes it of some use as a portable neutron source since there are few elements that produce neutrons all by themselves. Most transuranic elements must be placed in a nuclear reactor, must go through a series of decay processes, or must be mixed with other elements in order to give off neutrons. Cf-252 has a half-life of 2.65 years, and just one microgram (0.000001 grams) of the element produces over 170 mhhon neutrons per minute. 

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... 

Einsteinium belongs to group 13 (IIIA) of the heavy transuranic subseries of elements found in the actinide series. It was discovered after World War II, sometime in 1952, as a trace element in the residue from the massive explosion of the hydrogen bomb on Eniwetok... 

As with most other transuranic elements of the actinide series, fermium has an oxidation state of +3, as well as possibly a +2 oxidation state. Thus, this ion can combine with nonmetals, such as oxygen and the halogens, as do many of the other elements in this series. Two examples follow ... 

Nobelium is the next to last transuranic element of the actinide series. The transuranic elements are those of the actinide series that are heavier than uranium. Nobehum is also the heaviest element of the vertical group 16 (VIA). 

Lawrencium is the last of the transuranic elements and the 15 th in the actinide series (there are 15 elements in the lanthanide series as well, assuming you start counting the series at the elements lanthanide and actinium, respectively.) It is assumed that lawrencium has some chemical and physical characteristics similar to lutetium, located just above it in the lanthanide series. It is also located at the bottom of the group 17 (VILA) elements, which makes it the heaviest of the halides. 

Beyond element 92 (U) lie the transuranic elements of the actinide series. These are all artificial but 2< Pu is of interest because it is produced in nuclear reactors from 2 fU and may be released to the environment from accidents or weapons testing. It has a very long half life (2.4 x 104 years) and is a very dangerous alpha emitter, but, like radon, its geochemistry is too specialised to be included in this chapter. Choppin and Stout (1991) have written an overview of the general chemistry of Pu, to mark the 50th anniversary of its original isolation, and Rai et al. (1980) have discussed its soil chemistry. 

An additional material based on the extractant octyl-phenyl-N,N-diisobutyl-carbamoylmethylphosphine oxide, or CMPO, (marketed under the name TRU-Spec) has also been widely utilized for separations of transuranic actinides (Horwitz et al. 1993a) but is also useful for uranium-series separations (e.g., Burnett and Yeh 1995 Luo et al. 1997 Bourdon et al. 1999 Layne and Sims 2000). This material has even greater distribution coefficients for the uranium-series elements U (>1000), Th (>10000), and Pa. As shown in Figure 1, use of this material allows for sequential separations of Ra, Th, U, and Pa from a single aliquot on a single column. Separations of protactinium using this material (Bourdon et al. 1999) provide an alternative to liquid-liquid extractions documented in Pickett et al. (1994). 

Americium, Curium, and Californium Purification. These elements, together with any lanthanides in the sample or added as carriers, pass through the anion exchange column used to remove plutonium. This fraction is purified to remove natural-series radionuclides which interfere with americium, curium, or californium measurements as well as stable elements which plate with the transuranics and produce spectral degradation. This latter consideration is especially important for lanthanides as neodymium is used as a carrier. Two lanthanide/actinide separation cycles immediately before electroplating are essential for acceptable plate quality. 

Shortly after the discovery of transuranic elements about 50 years ago (see Morss and Fuger 1992), Seaborg suggested that the heaviest elements form a 5f transition series, which came to be known as the actinides, in analogy to the well known 4f series of the lanthanides. A glance at a modern periodic system of elements shows this basic concept to be still accepted, despite the fact that pronounced differences... 

Because the trivalent state exists for all the lanthanides and most of the actinides, variations in chemical properties with ionic radius are often compared for the two series. In general, those changes in crystal structure or other properties that depend on ionic size occur two elements earlier in the 4f series than in the Sf series. This is because the trivalent ion with a particular number of 5f electrons is larger, by about 0.03 A in the transuranic region, than the trivalent ion with an equal number of 4f electrons. 

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