Lanthanum, configuration

The lanthanides—or lanthanons, as they are sometimes called—are, strictly, the fourteen elements that follow lanthanum in the Periodic Table and in which the fourteen 4/electrons are successively added to the lanthanum configuration. Since the term lanthanide is used to indicate that these elements form a closely allied group, for the chemistry of which lanthanum is the prototype, the term is often taken as including lanthanum itself. Table 27-1 gives some properties of the atoms and ions. The electronic configuration are not all known with complete certainty owing to the great complexity o... 

The element lanthanum (atomic number 57) has the electronic configuration... 

Lanthanide elements, 411, 389 contraction, 413 electron configurations, 415 occurrence and preparation, 413 oxidation numbers, 414 properties, 412 Lanthanum... 

There is no essential difference between quenching via a MMCT state or a LMCT state. The latter occurs, for example, in Eu(III) if the LMCT state is either at low energy or if this state shows a large offset in the configurational coordinate diagram [23, 35]. The latter occurs in glasses [123], certain cryptates [124] and lanthanum compounds [125]. 

The rare earth (RE) ions most commonly used for applications as phosphors, lasers, and amplifiers are the so-called lanthanide ions. Lanthanide ions are formed by ionization of a nnmber of atoms located in periodic table after lanthanum from the cerium atom (atomic number 58), which has an onter electronic configuration 5s 5p 5d 4f 6s, to the ytterbium atom (atomic number 70), with an outer electronic configuration 5s 5p 4f " 6s. These atoms are nsnally incorporated in crystals as divalent or trivalent cations. In trivalent ions 5d, 6s, and some 4f electrons are removed and so (RE) + ions deal with transitions between electronic energy sublevels of the 4f" electroiuc configuration. Divalent lanthanide ions contain one more f electron (for instance, the Eu + ion has the same electronic configuration as the Gd + ion, the next element in the periodic table) but, at variance with trivalent ions, they tand use to show f d interconfigurational optical transitions. This aspect leads to quite different spectroscopic properties between divalent and trivalent ions, and so we will discuss them separately. 

Group 3 of the Periodic Table consists of the elements scandium, yttrium and either lanthanum or lutetium, depending upon the preferred arrangement of the Table. Group 3 elements have the outer electronic configuration ns2 p, and invariably their solution chemistry is that of the + 3 state. In this text, treatment of both La and Lu is carried out in Chapter 8, which deals with the f-block elements. Lanthanum and lutetium represent the first and last members of the lanthanide series. 

The lanthanide elements are the 15 elements from lanthanum to lutetium. Both La and Lu have been included to allow for the different versions of the Periodic Table, some of which position La in Group 3 as the first member of the third transition series and others that place Lu in that position. If Lu is considered to be the first element in the third transition series, all members of that series possess a filled shell 4f14 configuration. The outer electronic configurations of the lanthanide elements are given in Table 8.1. 

ACTINIUM- [CAS 7440-34-8]. Chemical element symbol Ac. at. no. 89. at. wt. 227 (mass number of the most stable isotope), periodic table group 3, classed in the periodic system as a higher homologue of lanthanum. The electronic configuration for actinium is... 

Rare Earth elements (REEs) elements that occur in the periodic table from lanthanum (La) to lutetium (Lu)—have similar chemical and physical properties due to their electronic configurations. 

Lanthanum, the first member of lanthanides has the configuration of 5d)6s2 and next member cerium, has 4fi6s2 while the next element praseodymium has the configuration 4f3 6s2. Although lanthanum itself does not possess any 4/electrons, it is customary to include this element in the series. The electronic configurations of the elements with fully filled (// and half-filled (f7)/-orbitals are relatively more stable. 

The extra stability of half-filled orbitals is seen in the elements europium (4 f 6s2) and gadolinium (4f 5d) 6s2). The element ytterbium has fully-filled /-orbitals with the configuration 4/4 6s2 and the extra electrons in lutetium goes in 5d orbitals (4/4 5dl 6s2). So except for lanthanum, gadolinium and lutetium which have a single electron in 5d orbitals the lanthanides do not have electron in the 5d orbitals. 

La(Mn,Ga)03 (225), and (La,Ba)(Mn,Ti)03 (308). With less than 50% cobalt, trivalent cobalt is diamagnetic Co111 ( 2). Ga3+ and Ti4+ are also diamagnetic. The electronic configuration of Ni111 may also be correlated with the lattice vibrations (quasistatic model). In Figure 60 are shown the ratios c/ /2a for the lanthanum sys-... 

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