Electron configuration rare earth elements

Symbol Gd atomic number 64 atomic weight 157.25 a lanthanide series rare earth element electron configuration 4/ 5di6s2 partially filled / orbital common oxidation state -i-3 six stable natural isotopes Gd-152 (0.2%), Gd-154 (2.86%), Gd-155 (15.61%, Gd-156 (20.59%), Gd-157 (16.42%), Gd-157 (23.45%)... 

Symbol Ho atomic number 67 atomic weight 164.93 a lanthanide series rare earth element electron configuration [Xe]4/ii6s2 valence state +3 metallic radius (coordination number 12) 1.767A atomic volume 18.78 cc/mol ionic radius Ho3+ 0.894A one naturally occurring isotope. Ho-165. 

Symbol Tb atomic number 65 atomic weight 158.925 a lanthanide series element an inner-transition rare earth metal electron configuration fXe]4/96s2 valence states -i-3, +4 mean atomic radius 1.782A ionic radii, Tb3+... 

Symbol Tm atomic number 69 atomic weight 168.93 a lanthanide series element a rare earth metal electron configuration iXe]4/i36s2 valence +2, -i-3 atomic radius 1.73 A ionic radius, Tm " " 1.09 A for coordination number 7 one stable, natural isotope Tm-169 (100%) thirty radioisotopes in the mass range 146-168, 170-176 ty, 1.92 years. 

According to this assignment the differentiating electron, that is, the final electron to enter the atom of lutetium, wss seen as an f electron. This suggested that lutetium should be the final element in the first row of the rare earth elements, in which f electrons are progressively filled, and not a transition element as had been believed by the chemists. As a result of more recent spectroscopic experiments the configuration of ytterbium has been altered to (27)... 

Indicate the position of the rare-earth elements in Mendeleev s periodic table, the electron configurations and sizes of their atoms, and their oxidation states. 

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. 

The Nd has the electron configuration [Xe]4f. Because it is a rare-earth element, spin-orbit coupling would be expected and hence, Eqs. 8.24-8.25 to apply. Furthermore, crystal-field splitting is usually unimportant for rare-earth ions because their partially filled 4f shells lie deep inside the ions, beneath filled 5s and 5p shells. Thus, the seven f orbitals would be degenerate and their occupancy would be a high-spin configuration, with the maximum value of S and L, in accordance with Hund s first and second rules ... 

The analytical chemistry of the transition elements see Transition Metals), that is, those with partly filled shells of d (see (f Configuration) or f electrons see f-Block Metals), should include that of the first transition period (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) and that of the second transition series (Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, and Ag). The third transition series embraces Hf, Ta, W, Re, Os, Ir, Pt, and An, and although it formally begins with lanthanum, for historical reasons this element is usually included with the lanthanoids (rare-earth elements) see Scandium, Yttrium the Lanthanides Inorganic Coordination Chemistry Rare Earth Elements). The actinoid elements see Actinides Inorganic Coordination Chemistry) are all radioactive see Radioactive Decay) and those with atomic number see Atomic Number) greater than uranium (Z = 92) are artificial the analytical chemistry of these elements is too specialized to consider here. 

Lanthanide elements (referred to as Ln) have atomic numbers that range from 57 to 71. They are lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). With the inclusion of scandium (Sc) and yttrium (Y), which are in the same subgroup, this total of 17 elements are referred to as the rare earth elements (RE). They are similar in some aspects but very different in many others. Based on the electronic configuration of the rare earth elements, in this chapter we will discuss the lanthanide contraction phenomenon and the consequential effects on the chemical and physical properties of these elements. The coordination chemistry of lanthanide complexes containing small inorganic ligands is also briefly introduced here [1-5]. 

Rare earth elements have similar configurations in the two outermost shells. They exhibit typical metallic properties in chemical reactions. They tend to lose three electrons and exhibit a 3+ valence state. From the Periodic Table of the elements, rare earth elements are classed as less reactive than alkali metals and alkaline earth metals but more reactive than other metals. They should be stored in an inert liquid otherwise they will be oxidized and lose their metal luster. The metal reactivity increases gradually from scandium to lanthanum and decreases gradually from lanthanum to lutetium. That is to say, lanthanum is the most reactive metal of the 17 rare earth elements. Rare earth metals can react with water and release hydrogen. They react more vigorously with acids but do not react with bases. 

The elements with atomic numbers from 57 (l thanum) to 71 (lutetium) are referred to as the lanthanide elements. These elements and two others, scandium and yttrium, exhibit chemical and physical properties very similar to lanthanum. They are known as the rare earth elements or rare earths (RE). Such similarity of the RE elements is due to the configuration of their outer electron shells. It is well known that the chemical and physical properties of an element depend primarily on the structure of its outermost electron shells. For RE elements with increasing atomic number, the first electron orbit beyond the closed [Xe] shell (65 remains essentially in place while electrons are added to the inner 4f orbital. Such disposition of electrons about the nucleus of the rare earth atoms is responsible for the small effect an atomic number increase from 57 to 71 has on the physical and chemical properties of the rare earths. Their assignment to the 4f orbital leads to slow contraction of rare earth size with increasing atomic number. The 4f orbitals of both europium and gadolinium are half occupied [Xe] (4F6s and [Xe] (4F5d 6s, so that there... 

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) ... 

The rare earth elements represent the largest subgroup in the periodic table and offer a unique, gradual variation of those properties which provide the driving force for various catalytic processes. Their peculiar electronic configuration and the concomitant unique physicochemical properties also have to be consulted for the purpose of synthetic considerations. The highly electropositive character of the lanthanide metals, which is comparable to that of the alkali and alkaline earth metals, leads as a rule to the formation of predominantly ionic compounds, Ln(III) being the most stable oxidation state [9]. This and other intrinsic properties are outlined in Scheme 1 which will serve as a point of reference in this section [10-13]. 

Nobelium is a member of the actinide series of elements. The ground state electron configuration is assumed to be (Rn)5fl47s2, by analogy with the equivalent lanthanide element ytterbium ([Kr]4fl46s2) there has never been enough nobelium made to experimentally verify the electronic configuration. Unlike the other actinide elements and the lanthanide elements, nobelium is most stable in solution as the dipositive cation No ". Consequently its chemistry resembles that of the much less chemically stable dipositive lanthanide cations or the common chemistry of the alkaline earth elements. When oxidized to No, nobelium follows the well-estabhshed chemistry of the stable, tripositive rare earth elements and of the other tripositive actinide elements (e.g., americium and curium), see also Actinium Berkelium Einsteinium Fermium Lawrencium Mendele-vium Neptunium Plutonium Protactinium Ruthereordium Thorium Uranium. 

Recently there has been a growing interest in catalytic properties of rare earths (R) and related compounds (Edelmann 1996, Hogerheide et al. 1996, Inumaru and Misono 1995, Taube 1995, Yasuda 1995, Imamoto 1994). Since rare-earth elements have specific electron configurations based on 4f orbitals, many intriguing reactions mediated by them which cannot be achieved by d-block transition metal compounds are expected to occur ... 

The vast majority of the molecular complexes of rare-earth elements (Sc, Y and La-Lu, hereafter abbreviated as R) are in trivalent state, which is the most stable. The oxidation state of the rare earths in these complexes is + 3, and the configuration of the Sc " ", and La + ions is that of the noble gases ([Ar], [Kr] and [Xe], respectively), and that of the remaining rare-earth tripositive ions (Ce to Lu +) is [Xe]4f 5d°6s° (n = l-14) while being formally in the valence shell, the f-electrons in these ions are very contracted and do not normally participate in bonding interactions, which are mostly ionic for all... 

However, there are many stable rare-earth compounds that are low-valent. The rare-earth elements are also early transition metals, in which d-electrons are in the valence shell. Since transition metal complexes in general exist in diverse oxidation states in which the electronic configuration is traditionally expressed as [NG]d s° with n>0 (NG being Ar, Kr or Xe), by analogy, there are a priori no reasons why R°, R and R complexes should not exist. Considering for instance the adjacent ions Hf " " and La which have the same electronic configuration ([Xe]5d 6s°), there are a few compounds of Hf (Fryzuk et al., 1996) and, as we shall see later, several perfectly characterised La complexes precisely in this electronic configuration. Until now, monovalent (R ) molecular compounds have only been found in the case of scandium, and there are several rare earths that can form zero-valent (R°) complexes. 

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