Electron lanthanide element

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

A predominant feature of the atomic structure of the lanthanide group is the sequential addition of 14 electrons to the 4f subshell (Table 1). The /"electrons do not participate in bond formation and in ordinary aqueous solutions all of the lanthanides exhibit a principal (III) state. The common (III) state confers a similarity in chemical properties to all lanthanide elements. Some of the lanthanides can also exist in the (II) state (Nd, Sm, Eu, Tm, Yh) or in the (IV) state (Ce, Pr, Nd, Tb, Dy). Except for Ce(IV), Eu(II), and Yb(II), these unusual lanthanide oxidation states can only be prepared under drastic redox pressure and temperature conditions, and they are not stable in aqueous solutions. Cerium (IV) is a strong oxidizing agent... 

Table 1—Oxidation states, electronic configurations, and radii of the (III) ion of the lanthanide elements and yttrium...

Would it require more energy to remove an electron from a 6s, 5d, or 4/ orbital from an atom of a lanthanide element Explain your answer and describe any special cases that may be encountered. 

The rare earth elements (REE) are the lanthanides (defined as those elements with valence electrons in 4/orbitals), La, Ce, Pr, Nd, (Pm), Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. Often included for analysis, because they behave in a chemically similar way, although strictly not REE, are the Group 3 transition metals Y and Lu. The radioactive lanthanide element promethium (Pm) is excluded from analysis, since it is not found in samples because of its short half-life. 

Hunt s group (50, 51) have pioneered the application of the Cl source to organometallics such as the iron tricarbonyl complex of heptafulvene, whose electron impact spectrum shows (M—CO)+ as the heaviest ion, in contrast to the methane Cl spectrum with the ion as base peak. Boron hydrides (52) and borazine (53) have also been studied. The methane Cl spectrum of arenechromium and -molybdenum (54) show protonation at the metal giving a protonated parent or molecular ion. Risby et al. have studied the isobutane Cl mass spectra of lanthanide 2,2,6,6-tetramethylheptane-3,5-dionates[Ln(thd)3] (55) and 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-oetanedione [H(fod)] lanthanide complexes (56). These latter complexes have been suggested as a means of analysis for the lanthanide elements. 

Symbol Nd atomic number 60 atomic weight 144.24 a rare earth lanthanide element a hght rare earth metal of cerium group an inner transition metal characterized by partially filled 4/ subshell electron configuration [Xe]4/35di6s2 most common valence state -i-3 other oxidation state +2 standard electrode potential, Nd + -i- 3e -2.323 V atomic radius 1.821 A (for CN 12) ionic radius, Nd + 0.995A atomic volume 20.60 cc/mol ionization potential 6.31 eV seven stable isotopes Nd-142 (27.13%), Nd-143 (12.20%), Nd-144 (23.87%), Nd-145 (8.29%), Nd-146 (17.18%), Nd-148 (5.72%), Nd-150 (5.60%) twenty-three radioisotopes are known in the mass range 127-141, 147, 149, 151-156. 

The lanthanide metals should also be investigated to higher pressures than previously applied. It is not excluded that their 4 f electrons also participate in bonding as do the 5 f s of Bk and Cf, after the dhcp, ccp and, possibly, distorted fee phases have been reached. An indication of this possibility can be seen in the recent discovery of the a-uranium structure type in praseodymium (Pr IV) . This structure type was previously observed for cerium, but was thought to be restricted to that metal which has an exceptional position among the lanthanide elements. 

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. 

Table 8.1 The outer electronic configurations of the lanthanide elements they all possess a 6s2 pair of electrons...

The layout of the periodic table (Fig. 2.5) reflects the shell structure of the electrons. Hydrogen and helium have only -shell electrons. The elements in row two have and L-shell electrons, with the Is orbitals always filled and the 2s and 2p orbitals filled in succession. Those in row three have and L-shell electrons, with Is, 2s, and 2p orbitals filled, and the 3 s and 3p orbitals are filled in succession. Elements in the fourth row have K, L, and M-shell electrons, with the Is, 2s, 3s, 2p, and 3p orbitals completely filled. After the 4s orbitals are filled, the 3d orbitals are filled, giving the transition metals. Then come the 4p orbitals. Row five is filled in an analogous fashion. In row six, the lanthanides, which fit between lanthanum and hafnium, reflect the appearance of the N-shell electrons, which fill the f orbitals. Row seven, which contains the actinides, also has K, L, M, and N-shell electrons. 

The atomic radii of the second- and third-series transition elements from group 4B on are nearly identical, though we would expect an increase in size on adding an entire principal quantum shell of electrons. The small sizes of the third-series atoms are associated with what is called the lanthanide contraction, the general decrease in atomic radii of the /-block lanthanide elements between the second and third transition series (Figure 20.4). 

Lanthanides are coextracted with actinides and then separated from actinides, which are forecasted to be sent to a repository. The lanthanide elements comprise a unique series of metals in the periodic table. These metals are distinctive in terms of size, valence orbitals, electrophilicity, and magnetic and electronic properties, such that some members of the series are currently the best metals for certain applications. Increased use of the lanthanides in the future is likely, because their unusual combination of physical properties can be exploited to accomplish new types of chemical transformations. These elements coextracted with actinides and then separated from the latter, could in the future be recovered and used (among the lanthanides, only 151Sm is a long-lived isotope (half-life 90 years)).4... 

The lanthanide elements were once known as the rare earths. Lanthanides, however, are not particularly rare. Holmium, one of the less common lanthanides, is still 20 times more abundant than silver on Earth. The rare earth name comes instead from how difficult it was for early chemists to separate all of the lanthanides from one another. Because these elements add electrons to an inner shell, they all show the same face to other elements. This makes them all react very similarly with other elements, and it can be tricky to tell them apart. 

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