Rare earth period

Schwetz et al. (1979) regarded the compound with a composition range of RCq 35 to RCo.65 as the monocarbide. They pointed out that this compound exists for the elements from samarium to the end of the rare earth period and for scandium as well as yttrium, and the lattice is face-centered cubic. The carbon atoms are isolated and appear no longer as pairs. Since a complete filling of the octahedron gaps with carbon atoms for rare earth metals is never achieved, the structure always remains strongly nonstoichiometric. Therefore, this type of compound is not a true monocarbide. 

According to Kyrki and Lokio (1971), most of the rare earth periodates are really hexaoxoiodates containing the H2l06 ions, and RIO5 4H2O should be... 

Infrared absorption frequenies of seleted rare earth periodates and iodates (Lokio, 1973 Lokio and... 

The infrared spectra of the rare earth periodates have been recorded by many authors. The frequencies at 1150-1200 cm (I lOH) and 3450-3500 cm (I OH) are particularly important because they are informative of the composition of the material (table 21) they do not appear for phases not containing the H2lOg ion. 

The periodic table also contains horizontal periods of elements, each period beginning with an element with an outermost electron in a previously empty quantum level and ending with a noble gas. Periods 1, 2 and 3 are called short periods, the remaining are long periods Periods 4 and 5 containing a series of transition elements whilst 6 and 7 contain both a transition and a rare earth senes,... 

Ion-exchange and complexing properties of organosilicon adsorbents were studied on the example of 50 elements of Periodical System. Among synthesized adsorbents it was found an effective complexation afents toward rare-earth elements. The sorption of elements is accompanied by bright display of tetradic effect. Adsorbents were synthesized, which opened wide chances of soi ption isolation and division of rare-earth elements. 

Just as the long fourth row of the periodic table arises from filling the 4s, 3d, and Ap orbitals, the fifth row, which also consists of eighteen elements, comes from filling the 5s, Ad, and 5p orbitals. In the sixth row, something new happens. After the 6s and the first one of the 5d electrons have entered, subsequent electrons go into the 4/orbitals. The fact that there are seven 4/ orbitals means that fourteen electrons can be accommodated in this manner. Filling the Af orbitals gives rise to a series of elements with almost identical chemical properties called the rare earth... 

The idealized configurations refer to those expected on the basis of Hund s rule, that is configurations in which spin multiplicity is maximized. The only elements where the idealized configurations are found to occur are Ce, Gd, and Lu. Many early assignments of rare earth configurations had assumed the above-given idealized versions, due to the predominant trivalency of the rare earths. This provides another example of a difference between the chemical and spectroscopic periodic tables. 

The problem is no longer the validity of Mendeleev s system, but the best way to represent it. Should it be the original short-form table with 8 columns, the familiar medium-long form with 18 columns, or perhaps even a long-form table with 32 columns, which more naturally accommodates the rare earth elements Into the main body of the table Altanahvely, some favor pyramidal tables, while others advocate the left-step form proposed by diaries Janet in the 1920s. Theodor Benfey and rhilip Stewart have proposed continuous spiral models. Hundreds, possibly even thousands, of periodic systems have been proposed, and each has its ardent supporters. 

The very long period is closely similar to the second long period, except for the interpolation of the rare-earth metals. It is interesting that a straight line can be passed through the points for barium, the two bivalent rare-earth metals, and the tetrahedral radii of the heavier elements. 

In this chapter, the results that have been obtained to date by the various techniques are reviewed. Sections 2 to 7 deal with metal elements in the same order as their periodic group classification, with the exception of the transition, rare earth and actinide elements which are dealt with in sections 8, 9 and 10, respectively. 

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... 

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