Actinium metal

Gr. aktis, aktinos, beam or ray). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Actinium-227, a decay product of uranium-235, is a beta emitter with a 21.6-year half-life. Its principal decay products are thorium-227 (18.5-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300-degrees G. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.6-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons. 

Actinium is found in uranium ores. An ore is a mineral mined for the elements it contains. Actinium is produced by the radioactive decay, or breakdown, of uranium and other unstable elements. Actinium can also be artificially produced. When radium is bombarded with neutrons, some of the neutrons become part of the nucleus. This increases the atomic weight and the instability of the radium atom. The unstable radium decays, gives off radiation, and changes to actinium. Actinium metal of 98 percent purity—used for research purposes—can be made by this process. 

The metallothermic reduction of halides was the first method to be successfully applied. Actinium metal can... 

From a solution containing iron and some rare earth metals, Debierne precipitated a mixture of hydroxides. It was radioactive, an activity that could not have its origin in uranium, radium or polonium. A new element could be isolated by fractional crystallization of magnesium lanthanum nitrate. The element was named actinium after the Greek word aktinos, meaning ray . Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300°C. 

With the exception of actinium, which is found naturally only in traces in uranium ores, these elements are by no means rare though they were once thought to be so Sc 25, Y 31, La 35 ppm of the earth s crustal rocks, (cf. Co 29ppm). This was, no doubt, at least partly because of the considerable difficulty experienced in separating them from other constituent rare earths. As might be expected for class-a metals, in most of their minerals they are associated with oxoanions such as phosphate, silicate and to a lesser extent carbonate. 

Between barium (Group 2, element 56) and lutetium (Group 3, element 71), the 4f orbitals fill with electrons, giving rise to the lanthanides, a set of 14 metals named for lanthanum, the first member of the series. The lanthanides are also called the rare earths, although except for promethium they are not particularly rare. Between radium (Group 2, element 88) and lawrenclum (Group 3, element 103), are the 14 actinides, named for the first member of the set, actinium. The lanthanides and actinides are also known as the inner transition metals. 

Americium (pronounced,, am-8- ris(h)-e-8m) is a man-made, radioactive, actinide element with an atomic number of 95. It was discovered in 1945. Actinides are the 15 elements, all of whose isotopes are radioactive starting with actinium (atomic number 89), and extending to lawrencium (atomic number 103). When not combined with other elements, americium is a silvery metal. Americium has no naturally occurring or stable isotopes. There are two important isotopes of... 

The radioactive element is a silvery, shiny, soft metal that is chemically similar to calcium and barium. It is found in tiny amounts in uranium ores. Its radioactivity is a million times stronger that that of uranium. Famous history of discovery (in a shed). Initially used in cancer therapy. Fatal side effects. Small amounts are used in luminous dyes. Radium was of utmost importance for research into the atom. Today its reputation is rather shaky as its decay gives rise to the unpleasant radon (see earlier). In nuclear reactors, tiny amounts of actinium are formed from radium. 

The 3rd group of the Periodic Table (the 1st column within the block of the transition elements) contains the metals scandium, yttrium, lanthanum, and actinium. Lanthanum (atomic number 57) may be considered the earliest member of the family of metals, called lanthanides (general symbol Ln), forming, inside the principal transition series, an inner transition series (up to atomic number 71). Scandium and yttrium together with the lanthanides are also called rare earth metals (general symbol R). 

Notice that by analogy with La and the lanthanides, similarly actinium (atomic number 89) and the following metals (up to atomic number 103) compose the family of actinides (general symbol An). 

Actinium is an extremely radioactive, silvery-white, heavy metal that glows in the dark with an eerie bluish hght. It decays rapidly which makes it difficult to study, given that it changes into thorium and francium through electron capmre and alpha decay. Its melting point is 1,051°C, its boding point is 3,198°C, and its density is 10.07g/cm. ... 

Actinium is the last (bottom) member of group 3 (IIIB) of elements in the periodic table and the first of the actinide series of metallic elements that share similar chemical and physical characteristics. Actinium is also closely related in its characteristics to the element lanthanum, which is located just above it in group 3. The elements in this series range from atomic number 89 (actinium) through 103 (lawrencium). Actiniums most stable isotope is actinium-227, with a half-life of about 22 years. It decays into Fr-223 by alpha decay and Th-227 through beta decay, and both of these isotopes are decay products from uranium-235. 

The metallic ion of actinium has an oxidation state of +3. Two examples of Ac compounds follow ... 

The actual situation with regard to the purity of most of the actinide metals is far from ideal. Only thorixun (99), uranium 11,17), neptunium 20), and plutonium 60) have been produced at a purity > 99.9 at %. Due to the many grams required for preparation and for accurate analysis, it is probable that these abundant and relatively inexpensive elements (Table I) are the only ones whose metals can be prepared and refined to give such high purities, and whose purity can be verified by accurate analysis. The purity levels achieved for some of the actinide metals are listed in Table II. For actinium (Ac), berkelium (Bk), californium (Cf),... 

This article presents a general discussion of actinide metallurgy, including advanced methods such as levitation melting and chemical vapor-phase reactions. A section on purification of actinide metals by a variety of techniques is included. Finally, an element-by-element discussion is given of the most satisfactory metallurgical preparation for each individual element actinium (included for completeness even though not an actinide element), thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, and einsteinium. 

Americium, californium, and einsteinium oxides have been reduced by lanthanum metal, whereas thorium has been used as the reductant metal to prepare actinium, plutonium, and curium metals from their respective oxides. Berkelimn metal could also be prepared by Th reduction of Bk02 or Bk203, but the quantity of berkelium oxide available for reduction at one time has not been large enough to produce other than thin foils by this technique. Such a form of product metal can be very difficult to handle in subsequent experimentation. The rate and yield of Am from the reduction at 1525 K of americium dioxide with lanthanum metal are given in Fig. 2. 

In principle, a promising method for the preparation of Ac metal is the tantalothermic reduction of AcC, as described generally in Section II,C. This method has not been tried as yet, however, so the metallothermic reduction of an actinium halide or oxide remains the only proved method. 

Actinium-227 occurs in uranium ore and is a decay product of uranium-235. It is found in equilibrium with its decay products. It is prepared hy homhard-ing radium atoms with neutrons. Chemically, the metal is produced hy reducing actinium fluoride with lithium vapor at 1,100°C to 1,300°C. 

Ac, actinium, was initially identified in 1899 by Andr6-Louis Debierne, a French chemist, who separated it from pitchblende. He dissolved the mineral in acid, then added NH4OH, and found that a radioactive species was carried down with the rare earth hydroxides. He named the element actinium after the Greek aktinos which means ray. Because of its low abundance in U, the element is usually not obtained by isolation from U. It can be obtained in mlligram amounts by irradiation of Ra-226 in a nuclear reactor. The preparation of Ac metal involves reduction of AcFs by Li at high temperature. 

In this treatment, the line connecting the metallic radii of actinium and curium is considered as representative of an actinide contraction, analogous to the lanthanide contraction. This actinide contraction line may be considered as a trivalent basis line as for lanthanides therefore, the considerable departure to a lower value for the metallic... 

Although the theoretical studies predict solvent medium breakdown before the onset of actinium electrodeposition, there have been reports of Ac(0) electrodeposition from aqueous solutions utilizing several different methods [8, 9]. One set of studies [8] describes the electrodeposition of actinium from nitric acid solutions, with varying pH values (1.0-4.0) being set to the appropriate level by the addition of sodium hydroxide. The anode and cathode in these studies were platinum metal, and the current density was varied from 50 to 200 mA cm . The authors found that quantitative electrodeposition of actinium could be achieved under various conditions, with the shortest electrolysis time of 1 h being obtained with a current density of200 mA cm and a pH of 2.0. A second study employed a saturated aqueous solution of urea oxalate (ca 6.6% at 30 °C) as an electrolyte for the electrodeposition of Ac onto a nickel foil cathode [9]. The authors of this study found that the yield of electrodeposited Ac increased with time and reached a near quantitative maximum yield of 97% at a current density of 53 mAcm after 2 h. The Ac electrodeposits were suitable for further study using nuclear spectroscopy. 

In 1949, about half a century after the discovery of actinium, the International Rare Metals Refinery, Inc. produced it industrially (134). It is about 150 times as active as radium and is a valuable source of neu-... 

The seventh-period inner transition metals are called the actinides because they fall after actinium, Ac. They, too, all have similar properties and hence are not easily purified. The nuclear power industry faces this obstacle because it requires purified samples of two of the most publicized actinides uranium, U, and plutonium, Pu. Actinides heavier than uranium are not found in nature but are synthesized in the laboratory. 

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