Electron configurations heavy elements

Let X be an element of the fourth to seventh main groups of the periodic table, i.e. an element that tends to attain the electronic configuration of the following noble gas by taking up electrons (the heavy elements of the third main group may also be included). An X atom has e(X) valence electrons. 

The loose connection between electron configuration and the chemical behaviour of the heavy elements (transuranics). C. K. Jorgensen, Angew. Chem., Int. Ed. Engl., 1973,12,12-19 (73). 

Chromium has a similar electron configuration to Cu, because both have an outer electronic orbit of 4s. Since Cr3+, the most stable form, has a similar ionic radius (0.64 A0) to Mg (0.65 A0), it is possible that Cr3+ could readily substitute for Mg in silicates. Chromium has a lower electronegativity (1.6) than Cu2+ (2.0) and Ni (1.8). It is assumed that when substitution in an ionic crystal is possible, the element having a lower electronegativity will be preferred because of its ability to form a more ionic bond (McBride, 1981). Since chromium has an ionic radius similar to trivalent Fe (0.65°A), it can also substitute for Fe3+ in iron oxides. This may explain the observations (Han and Banin, 1997, 1999 Han et al., 2001a, c) that the native Cr in arid soils is mostly and strongly bound in the clay mineral structure and iron oxides compared to other heavy metals studied. On the other hand, humic acids have a high affinity with Cr (III) similar to Cu (Adriano, 1986). The chromium in most soils probably occurs as Cr (III) (Adriano, 1986). The chromium (III) in soils, especially when bound to... 

EINSTENIUM. CAS 7429-92-71. Chemical element symbol Es, at. no. 99. at. wt. 254 (mass number of the most stable isotope), radioactive metal of the Actinide series, also one of the Transuranium elements. Both einsteinium and fermium were formed tit a thermonuclear explosion that occurred in the South Pacific in 1952. The elements were identified by scientists from the University of California s Radiation Laboratory- the Argonnc National Laboratory, and the I. os Alamos Scientific Laboratory. It was observed that very heavy uranium isotopes which resulted from the action of the instantaneous neutron dux on uranium (contained in the explosive device) decayed to form Es and Fm. The probable electronic configuration of Es is... 

In summary, it appears that the chemical activity of the elements is based primarily on electron configuration and then on outermost electron distance from the nucleus. Mostly because of their electron configuration, the transition metals, in the middle of the periodic table (next to the noble gases), are the most stable elements. They are not very reactive with other elements. This is why these transition metals, the so-called heavy metals, make such good jewelry material. However, other important factors are their shiny luster, ductility, and malleability. 

Since spin-orbit coupling is very important in heavy element compounds and the structure of the full microscopic Hamiltonians is rather complicated, several attempts have been made to develop approximate one-electron spin-orbit Hamiltonians. The application of an (effective) one-electron spin-orbit Hamiltonian has several computational advantages in spin-orbit Cl or perturbation calculations (1) all integrals may be kept in central memory, (2) there is no need for a summation over common indices in singly excited Slater determinants, and (3) matrix elements coupling doubly excited configurations do not occur. In many approximate schemes, even the tedious four-index transformation of two-electron integrals ceases to apply. The central question that comes up in this context deals with the accuracy of such an approximation, of course. 

Conceptually, it is the atomic number and the electronic configuration of an element that define its position in the Periodic Table. Since they cannot be measured for the very heavy elements, information on its chemical behavior is often used to place an element in a chemical group. Unfortunately, with increasing nuclear charge the cross sections and the production rates drop so rapidly that such chemical information can be accessed only for elements with a half-life of the order of at least few seconds and longer. In this case, some fast chemistry techniques are used. They are based on the principle of chromatographic separations either in the gas phase exploiting the differences in volatility of heavy element compounds, or in the aqueous... 

Most of the present discussion has been concerned with applications of REPs within the framework of otherwise essentially orbital-based calculations. On the other hand, a recent application 110) involved a quantum Monte Carlo (QMC) procedure. [A useful overview of Monte Carlo electronic structure work has been given by Ceperly and Alder 111). ] Currently, QMC offers little, if any, competition for conventional calculations in that the computer time required to reduce statistical errors to acceptable limits increases rapidly as a function of atomic number and is excessive for all but the smallest systems. Recent fluorine calculations required nearly 100 hours of supercomputer time 112). Although, on the surface, it would appear totally impractical, the appeal of this approach in the context of heavy-element work is its avoidance of extensive basis sets and enormous configuration expansions that plague present studies. 

Tn accordance with its electronic configuration and the resulting posi-tion in the periodic system of elements the actinide element americium is the heavy homolog of the rare earth element europium (14) ... 

Element 39, with 4d 5s2 electron configuration, is also similar to the lanthanides. It occurs with the lanthanides in minerals the best source is xenotime, YPO4. Yttrium has properties approximately midway between those of Sc and La its compounds also resemble those of the heavy earths dysprosium and holmium, the ionic radius (0.90 A) being similar. 

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