Europium physical properties

After the discovery of plutoninm and before elements 95 and 96 were discovered, their existence and properties were predicted. Additionally, chemical and physical properties were predicted to be homologous (similar) to europium (gjEu) and gadolinium ( Gd), located in the rare-earth lanthanide series just above americium (gjAm) and curium ((,jCm) on the periodic table. Once discovered, it was determined that curium is a silvery-white, heavy metal that is chemically more reactive than americium with properties similar to uranium and plutonium. Its melting point is 1,345°C, its boihng point is 1,300°C, and its density is 13.51g/cm. ... 

Ionic radius Eir 1.09 A, F.u1 (1.950 A. Metallic radius 1.995 A. First ionization potential 5.67 cV second 11.25 eV. Oxidation potential F.u -> F.uv + e". 0.43 V. Other important physical properties of europium are given under Rare-Earth Elements and Metals. 

The metals are relatively high-melting and -boiling. Their physical properties usually show smooth transition across the series, except that discontinuities are often observed for the metals that have a stable -1-2 state, europium and ytterbium. Thus the atomic radii of europium and ytterbium are about 0.2 A greater than might be predicted by interpolation from values for the flanking lanthanides (Figure 3.1). 

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]. 

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... 

The materials derived from YBa2Cu307 by replacing yttrium with other rare earth elements (lutetium, ytterbium, thulium, erbium, hohnium, dysprosium, gadolinium, europium, samarium, neodymium, lanthanum) are also superconductors, with r, s of 88 to 96 K. The crystal structures of RBa2Cu307 are almost the same as those of YBa2Cu307. The lattice constant is slightly different for the different ionic radii of the rare earth elements, and yet their chemical and physical properties are almost the same as those of YBa2Cu307. 

The atomic volumes of the lanthanides, as calculated from their room-temperature lattice parameters, are shown in fig. 3. Basically this is the same plot as given by Klemm and Bommer where the lanthanide contraction is evident, and also the anomalous valence states for cerium (slightly greater than three) and europium and ytterbium (both divalent). Anomalies due to divalency are also evident in many of the physical properties and these will be duly noted throughout the chapter. The occurrence of divalency in europium and ytterbium is a striking confirmation of Hund s rule that half-filled (in the case of divalent europium with a 4f con-... 

In Chapters I and 2, an introduction is made to the synchrotron Mossbauer spectroscopy with examples. Examples include the/ns/tu Mossbauer spectroscopy with synchrotron radiation on thin films and the study of deep-earth minerals. Investigations of in-beam Mossbauer spectroscopy using a Mn beam at the RIKEN RIBF is presented in Chapter 3. This chapter demonstrates innovative experimental setup for online Mossbauer spectroscopy using the thermal neutron capture reaction, Fe (n, y) Fe. The Mossbauer spectroscopy of radionuclides is described in Chapters 4-7. Chapter 4 gives full description of the latest analysis results of lanthanides Eu and Gd) Mossbauer structure and powder X-ray diffraction (XRD) lattice parameter (oq) data of defect fluorite (DF) oxides with the new defect crystal chemistry (DCC) Oq model. Chapter 5 reviews the Np Mossbauer and magnetic study of neptunyl(+l) complexes, while Chapter 6 describes the Mossbauer spectroscopy of organic complexes of europium and dysprosium. Mossbauer spectroscopy is presented in Chapter 7. There are three chapters on spin-state switching/spin-crossover phenomena (Chapter 8-10). Examples in these chapters are mainly on iron compounds, such as iron(lll) porphyrins. The use of Mossbauer spectroscopy of physical properties of Sn(ll) is discussed in Chapter I I. 

The dipositive oxidation state is unusual among the lanthanides. The more easily available divalent species are europium, ytterbium and samarium, although other divalent lanthanide compounds are known. Several reviews dealing, at least partly, with divalent lanthanides can be found in the literature. The most recent and detailed paper is that of Johnson (1977), which includes preparations and physical properties. Two other reviews are also available (Asprey et al., 1960 Marks, 1978). Thermochemical properties have been reviewed by Morss (1976). 

Xin, H., Li, E.Y, Guan, M., etal. (2003) Carbazole-functionalized europium complex and its high-efficiency organic electroluminescent properties. Journal of Applied Physics, 94, 4729-4731. 

The major breakthrough occurred in 1953 when the Ames Laboratory team (Daane et al. 1953) reported the preparation of samarium, europium and ytterbium in high purity and high yields by the reduction of their oxides with lanthanum metal in a vacuum. With the preparation of samarium metal, finally, 126 years after the first rare earth element was reduced to its metallic state, all of the naturally occurring rare earths were now available in their elemental state in sufficient quantity and purity to measure their physical and chemical properties. The success of this reaction is due to the low vapor pressure of lanthanum and the extremely high vapor pressures of samarium, europium and ytterbium (Daane 1951, 1961, Habermann and Daane 1961). It is interesting to note that this same technique has been the method of choice for the preparation of some transplutonium metals (Cunningham 1964). 

Sm(lll) has a similar resonance energy level as Eu(lll). The physical and chemical properties of the two ions are also similar [11]. So samarium complexes emit fluorescence in the same sequence as that of europium complexes with different p-diketone ligands. Tb(IIl) has a higher resonance energy level. The fluorescence of Tb(Ill) complexes decrease in a different way to that of Eu(lll) and Sm(lll) complexes. Tb(acac)3Phen emits the most intense fluorescence in the terbium complexes. The reason is that the triplet state of acac is 25300 cm, much higher... 

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