Actinoids Uranium

Compounds with Sc, Y, lanthanoids and actinoids are of three types. Those with composition ME have the (6-coordinated) NaCl structure, whereas M3E4 (and sometimes M4E3) adopt the body-centred thorium phosphide structure (Th3P4) with 8-coordinated M, and ME2 are like ThAsi in which each Th has 9 As neighbours. Most of these compounds are metallic and those of uranium are magnetically ordered. Full details of the structures and properties of the several hundred other transition metal-Group 15 element compounds fall outside the scope of this treatment, but three particularly important structure types should be mentioned because of their widespread occurrence and relation to other structure types, namely C0AS3,... 

The analytical chemistry of the transition elements see Transition Metals), that is, those with partly filled shells of d (see (f Configuration) or f electrons see f-Block Metals), should include that of the first transition period (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) and that of the second transition series (Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, and Ag). The third transition series embraces Hf, Ta, W, Re, Os, Ir, Pt, and An, and although it formally begins with lanthanum, for historical reasons this element is usually included with the lanthanoids (rare-earth elements) see Scandium, Yttrium the Lanthanides Inorganic Coordination Chemistry Rare Earth Elements). The actinoid elements see Actinides Inorganic Coordination Chemistry) are all radioactive see Radioactive Decay) and those with atomic number see Atomic Number) greater than uranium (Z = 92) are artificial the analytical chemistry of these elements is too specialized to consider here. 

Americium is called an actinoid or transuranium element. It occurs in Row 7 of the periodic table, a chart that shows how the chemical elements are related to each other. The actinoids are named after element 89, actinium. The term transuranium means beyond uranium in the periodic table. Uranium has an atomic number of 92. Any element with an atomic number larger than 92, therefore, is called a transuranium element. 

Uranium is the heaviest and last naturally occurring element in the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. Uranium occurs near the beginning of the actinoid family. The actinoid family consists of elements with atomic numbers 89 through 103. 

The actinides, or actinoids, have atomic numbers between 89 and 102 and are named for the first element in that series, actinium. The actinides are often called the transuranium elements and include the three heaviest naturally occurring elements in the periodic table—thorium, protactinium, and uranium. Protactinium is rare, but uranium and thorium are found in significant amounts in the Earths crust. The remaining actinides are synthetic, which means they are produced through artificial means. 

The lanthanoids resemble each other much more closely than do the members of a row of t/-block metals. The chemistry of the actinoids is more complicated, and in addition, only Th and U have naturally occurring isotopes. Studies of the transuranium elements (those with Z > 92) require specialized techniques. The occurrence of artihcial isotopes among the /-block elements can be seen from Appendix 5 all the actinoids are unstable with respect to radioactive decay (see Section 24.9), although the half-lives of the most abundant isotopes of thorium and uranium ( Th and t = 1.4 x lO and 4.5 x 10 yr respectively) are... 

In the remaining sections, we focus on the chemistries of thorium and uranium (the actinoids for which the most extensive chemistries have been developed) and plutonium. Potential diagrams for Np, Pu and Am are included in Figure 24.6. 

There have only been a few dithiocarboxylato complexes of lanthanoid and actinoid atoms. Only the samarium and uranium complexes have been crys-tallographically analyzed among such complexes, although the formations and spectral studies of a few lanthanum [117], cerium [48,117] and thorium [117,118] complexes have been reported. 

Of the actinoids, only uranium and thorium occur naturally in significant quantities. The naturally occurring isotopes of... 

THE ACTINIDE ELEMENTS (actinoids) comprise the 14 elements with atomic numbers 90-103, which follow actinium in the periodic table thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), berkelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), mendele-vium (Md), nobelium (No), and lawrencium (Lr). The actinides constitute a unique series of elements which are formed by the progressive filling of the 5/ electron shell. Although not formally an actinide element, actinium (Ac ... 

One series of 15 elements, known as the actinoids, is removed from this period and placed at the bottom of the periodic table. Uranium is an actinide element. 

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