Actinium chemistry

As the parent of actinium in this series it was named protoactinium, shortened in 1949 to protactinium. Because of its low natural abundance its chemistry was obscure until 1960 when A. G. Maddock and co-workers at the UK Atomic Energy Authority worked up about 130g from 60 tons of sludge which had accumulated during the extraction of uranium from UO2 ores. It is from this sample, distributed to numerous laboratories throughout the world, that the bulk of our knowledge of the element s chemistry was gleaned. 

The most interesting elements of the seventh row are those following actinium. For some of these elements a large amount of chemistry is known. The first four, actinium, thorium, protactinium, and uranium, used to be shown in the periodic... 

The chemistry of neptunium (jjNp) is somewhat similar to that of uranium (gjU) and plutonium (g4Pu), which immediately precede and follow it in the actinide series on the periodic table. The discovery of neptunium provided a solution to a puzzle as to the missing decay products of the thorium decay series, in which all the elements have mass numbers evenly divisible by four the elements in the uranium series have mass numbers divisible by four with a remainder of two. The actinium series elements have mass numbers divisible by four with a remainder of three. It was not until the neptunium series was discovered that a decay series with a mass number divisible by four and a remainder of one was found. The neptunium decay series proceeds as follows, starting with the isotope plutonium-241 Pu-24l—> Am-24l Np-237 Pa-233 U-233 Th-229 Ra-225 Ac-225 Fr-221 At-217 Bi-213 Ti-209 Pb-209 Bi-209. 

Organic Chemistry—Revision Notes, http //www.revision-notes.co.uk/revision/130.html (accessed October 5, 2005). Periodic Table Actinium, http //www.chemicalelements.com/elements/ac.html (accessed September 6> 2005). 

One of the most important observations of atoms is the set of relationships between elements that belong to one of the series of radioactive decays. The parent elements of uranium, thorium and actinium decay through many intermediates to the stable element lead. The Nobel Prize in Chemistry for 1921 was awarded in 1922 to Frederick Soddy for his complete characterization of these processes. The story is beautifully told in his Nobel Lecture entitled The origins of the conception of isotopes (25). 

The aqueous chemistry of the two rows of f-block elements, the lanthanides (lanthanum to lutetium) and the actinides (actinium to lawrencium), are sufficiently different from each other to be dealt with in separate sections. Similarities between the two sets of elements are described in the actinide section. 

Hageman, F. The Chemistry of Actinium , in G.T. Seaboig and J.J. Katz (editors), The Actinide Elements, National Nuclear Energy Series, IV-14A, p. 14, McGraw-Hill, New York, NY, 1954. 

Beyond element 121, eka-actinium, a series of 6f elements may occur, in analogy to the 5/ actinidc elements following actinium. But the 5g orbital -the first g orbital at all - may be filled in competition. Consequently, a series of 32 superactinide elements [20] may exist in which inner electron shells are filled whereas the configuration of the valence electrons remains unchanged. The chemistry of such elements [14,15] would be most exciting. 

A tiny amount of a very unstable species (half-life, 21 minutes) has been detected among the decay products of actinium tracer experiments by Mile. M. Perey showed that this species has the same chemistry as that of cesium and is presumably the heaviest alkali metal. It is named francium after Mile. Perey s homeland. 

Moseley then played with a problem concerning the life of an emanation of actinium, one of the radioactive elements. This period was so short that special, delicate devices had to be constructed to detect it. Together with the Polish scientist, K. Fajans, Professor of Chemistry at the University of Munich, he solved the question. The average life of the emanation was less than one five-hundredth of a second. 

The general chemistry of Ac3 in both solid compounds and solution, where known, is very similar to that of lanthanum, as would be expected from the similarity in position in the Periodic Table and in radii (Ac3, 1.10 La3, 1.06 A) together with the noble gas structure of the ion. Thus actinium is a true member of Group 3, the only difference from lanthanum being in the expected increased basicity. The increased basic character is shown by the stronger absorption of the hydrated ion on cation-exchange resins, the poorer extraction of the ion from concentrated nitric acid solutions by tributyl phosphate, and the hydrolysis of the trihalides with water vapor at 1000°C to the oxohalides AcOX the lanthanum halides are hydrolyzed to oxide by water vapor at 1000°C. 

Since the chemistry of actinium is confined to the Ac + ion, it can readily be separated from thorium (and the lanthanides, for that matter) by processes like solvent extraction with thenoyltrifluoroacetone (TTFA) and by cation-exchange chromatography. The latter is an excellent means of purification, as the Ac + ion is much more strongly bound by the resin than its decay products. 

The f-block elements comprise two series of inner transition elements which appear, firstly after lanthanum and secondly after actinium, in the Periodic Table. The elements from cerium to lutetium are known as the lanthanides and, because of its chemical similarity to these elements, lanthanum is usually included with them. Scandium and yttrium also show strong chemical similarities to the lanthanides, so that the chemistry of these elements is also often considered in conjunction with that of the lanthanide series. The second series of f-block elements, from thorium to lawrencium, is known as the actinide series and again it is usual to consider actinium together with this series. 

K. W. Bagnall, Chemistry of the Rare Radioelements (Polonium, Actinium), Butterworths, London, 1957... 

Pure and Applied Chemistry (lUPAC), the governing body that officially confirms and names any new elements. The lUPAC lists the atomic weight in brackets when an element does not have any stable nuclides. For example, the atomic weight of actinium is listed as [227]. This represents the mass of its longest-lived isotope. 

The solution photochemistry of the actinides begins with uranium none has been reported for actinium, thorium, and protactinium. Spectra have been obtained for most of the actinide ions through curium in solution (5). Most studies in actinide photochemistry have been done on uranyl compounds, largely to elucidate the nature of the excited electronic states of the uranyl ion and the details of the mechanisms of its photochemical reactions (5a). Some studies have also been done on the photochemistry of neptunium (6) and plutonium (7). Although not all of these studies are directed specifically toward separations, the chemistry they describe may be applicable. 

The name comes from the Greek aktis, meaning beam or ray. It was discovered by Andre-Louis Debierne (1874-1949) in 1899 and independently by Fritz Giesel (1852-1927) in 1902. It exists in very small quantities in association with uranium ores. Actinium has few uses outside the laboratory, but its discovery was important for the development of chemistry and physics, as it was one of the materials used to study radioactive decay, since it breaks down into thorium, radium, radon, bismuth, polonium, and isotopes of lead. 

In 1945 Glenn Seaborg proposed that actinium was the first member of a family of fifteen elements (the actinides ), characterized by the possession of the 5/orbitals. His proposal was based on the similarity of the chemistry of actinium to that of lanthanum (atomic number 57), which is the first member of the fifteen elements of the trivalent lanthanide family. Actinium is somewhat more basic than lanthanum but, like lanthanum, forms compounds that have strongly ionic bonds. Many actinium compounds are... 

Nobelium is a member of the actinide series of elements. The ground state electron configuration is assumed to be (Rn)5fl47s2, by analogy with the equivalent lanthanide element ytterbium ([Kr]4fl46s2) there has never been enough nobelium made to experimentally verify the electronic configuration. Unlike the other actinide elements and the lanthanide elements, nobelium is most stable in solution as the dipositive cation No ". Consequently its chemistry resembles that of the much less chemically stable dipositive lanthanide cations or the common chemistry of the alkaline earth elements. When oxidized to No, nobelium follows the well-estabhshed chemistry of the stable, tripositive rare earth elements and of the other tripositive actinide elements (e.g., americium and curium), see also Actinium Berkelium Einsteinium Fermium Lawrencium Mendele-vium Neptunium Plutonium Protactinium Ruthereordium Thorium Uranium. 

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