The lanthanides and actinides

The sixth row of the periodic table begins with Cs and Ba, which have [Xe]6s and [Xe]6s configurations, respectively. Notice, however, that the periodic table then has a break, with elements 57-70 placed below the main portion of the table. This break point is where we begin to encounter a new set of orbitals, the 4f. 

There are seven degenerate 4/orbitals, corresponding to the seven allowed values of mi, ranging from 3 to —3. Thus, it takes 14 electrons to fill the 4/orbitals completely. The 14 elements corresponding to the filling of the 4/orbitals are known as either the lanthanide elements or the rare earth elements. These elements are set below the 

Because the energies of the 4/and 5d orbitals are very close to each other, the electron configurations of some of the lanthanides involve 5d electrons. For example, the elements lanthanum (La), cerium (Ce), and praseodymium (Pr) have the following electron configurations  

Because La has a single 5d electron, it is sometimes placed below yttrium (Y) as the first member of the third series of transition elements Ce is then placed as the first member of the lanthanides. Based on their chemistry, however. La can be considered the first element in the lanthanide series. Arranged this way, there are fewer apparent exceptions to the regular filling of the 4/ orbitals among the subsequent members of the series. 

After the lanthanide series, the third transition element series is completed by the filling of the 5d orbitals, followed by the filling of the 6p orbitals. This brings us to radon (Rn), heaviest of the known noble-gas elements. 

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As regards the transition elements, the first row in particular show some common characteristics which define a substantial part of their chemistry the elements of the lanthanide and actinide series show an even closer resemblance to each other. 

There is no single best form of the periodic table since the choice depends on the purpose for which the table is used. Some forms emphasize chemical relations and valence, whereas others stress the electronic configuration of the elements or the dependence of the periods on the shells and subshells of the atomic structure. The most convenient form for our purpose is the so-called long form with separate panels for the lanthanide and actinide elements (see inside front cover). There has been a lively debate during the past decade as to the best numbering system to be used for the individual... 

The three series of elements arising from the filling of the 3d, 4d and 5d shells, and situated in the periodic table following the alkaline earth metals, are commonly described as transition elements , though this term is sometimes also extended to include the lanthanide and actinide (or inner transition) elements. They exhibit a number of characteristic properties which together distinguish them from other groups of elements ... 

Unsubstituted bisphthalocyanines 2 are formed in the presence of several elements which exist in a stable oxidation state of + III or +IV such as titanium, zirconium, hafnium, indium and most of the lanthanide and actinide elements. 

The quantum chemistry of unusual oxidation states of the lanthanides and actinides. V. I. Spitsyn and G. V. Ionova, Russ. Chem. Rev. (Engl. Transl.), 1984, 53, 725 (138). 

Thus the rather easily obtained atomic sizes are the best indicator of what the f-electrons are doing. It has been noted that for all metallic compounds in the literature where an f-band is believed not to occur, that the lanthanide and actinide lattice parameters appear to be identical within experimental error (12). This actually raises the question as to why the lanthanide and actinide contractions (no f-bands) for the pure elements are different. Analogies to the compounds and to the identical sizes of the 4d- and 5d- electron metals would suggest otherwise. The useful point here is that since the 4f- and 5f-compounds have the same lattice parameters when f-bands are not present, it simplifies following the systematics and clearly demonstrates that actinides are worthy of that name. 

Brown, D. "Halides of the Lanthanides and Actinides" Wiley-Interscience, London-New York-Sydney, 1968. 

Hydrous Oxides and Hydroxides in the Lanthanide and Actinide Series, Final Report June 1, 1969-May 31, 1972. U.S. AEC Report 0R0-3955-3, Oak Ridge Operation Office, Oak Ridge, TN, 1972. 

In the lanthanide and actinide series, arguments like these are greatly eased by the very small ligand field effects. Consider the reaction... 

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. 

Here we try to gain insight into the trends in reactivity of the metals without getting lost in too much detail. We therefore invoke rather crude approximations. The electronic structure of many metals shows numerous similarities with respect to the sp band, with the metals behaving essentially as free-electron metals. Variations in properties are due to the extent of filling of the d band. We completely neglect the lanthanides and actinides where a localized f orbital is filled, as these metals hardly play a role in catalysis. 

VIIIB, with the number of (outer) d electrons plus two for the transition elements, and the number of (outer) / electrons plus three for the lanthanides and actinides. 

Atoms or ions with completely filled orbitals have J equal to zero, which means that atoms with closed shells have no magnetic moment. The only atoms that display a magnetic moment are those with incompletely filled shells. These are particularly found in the transition metals, with incompletely filled d shells, and the lanthanides and actinides, which have incompletely filled/shells. 

The lanthanide and actinide ions react with oxygen donor molecules. Recently, four selected lanthanide and actinide ions have been reacted with several sources of oxygen including 02. The formation of [MO]+ and [M02]+ ions were observed by the reactions of Ce+, Nd+, Th+, and U+ with 02. All reactions produced [MO]+ but [MOH]+ was a common minor product and [Th02]+ and [U02]+ ions were also obtained by the reaction of M+ with 02 (101). 

The lanthanides and actinides are two series of fourteen elements, the members of each series having very similar properties. How do you account for these similarities, and for the fact that all the elements are metals ... 

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