Lutetium atomic radius

The atomic radii of the second row of d-metals (Period 5) are typically greater than those in the first row (Period 4). The atomic radii in the third row (Period 6), however, are about the same as those in the second row and smaller than expected. This effect is due to the lanthanide contraction, the decrease in radius along the first row of the / block (Fig. 16.4). This decrease is due to the increasing nuclear charge along the period coupled with the poor shielding ability of /-electrons. When the d block resumes (at lutetium), the atomic radius has fallen from 217 pm for barium to 173 pm for lutetium. 

Use the data from Appendix E to graph the variation of atomic radius with atomic number for the rare-earth elements from lanthanum to lutetium. 

Abstract This chapter discusses the chemical and physical properties of the lanthanides, some of which are in a certain way peculiar. It discusses the oxidation states of the REE, and the phenomenon called the lanthanide contraction (meaning that the atomic radius decreases with increasing atomic number in the series lanthanum-lutetium). It lists the isotopes known per element, and explains the radioactivity of promethium, the only element of the rare earths that has only radioactive isotopes and no stable isotopes. Magnetism and luminescence also are discussed. 

In the periodic system, the lanthanide group of elements also gives rise to a peculiar phenomenon, called the lanthanide contraction. This phenomenon is the important and progressive decrease in atomic radii and in radii of ions when going from lower to higher atomic numbers in the lanthanide series. Thus lanthanum has the largest atomic radius, and lutetium has the smallest. In Table 3.3, the ionic radii for the lanthanides are given, and the effect described above can be clearly seen in Fig. 3.2. 

Comparison of the predictions of this scheme with the data for the diamagnetic sesquioxides of lanthanum and lutetium (193) suggests that if all of the entropy variation is to be ascribed to the cation, the contributions would have to decrease with increasing mass (or atomic number) from 15.2 for lanthanum to 13.0 for lutetium. As an approximation, the decrease is taken proportional to that of the cationic radius obtained by x-ray diffraction measurements. The following (improved) values then apply ... 

Most trace elements have values of D< C 1, simply because they differ substantially either in ionic radius or ionic charge, or both, from the atoms of the major elements they replace in the crystal lattice. Because of this, they are called incompatible. Exceptions are trace elements such as strontium in plagioclase, ytterbium, lutetium, and scandium in garnet, nickel in olivine, and scandium in clinopyroxene. These latter elements acmally fit into their host crystal structures slightly better than the major elements they replace, and they are therefore called compatible. Thus, most chemical elements of the periodic table are trace elements, and most of them are incompatible only a handful are compatible. 

The lanthanide or rare earth elements (atomic numbers 57 through 71) typically add electrons to the 4f orbitals as the atomic number increases, but lanthanum (4f°) is usually considered a lanthanide. Scandium and yttrium are also chemically similar to lanthanides. Lanthanide chemistry is typically that of + 3 cations, and as the atomic number increases, there is a decrease in radius for each lanthanide, known as the lanthanide contraction. Because bonding within the lanthanide series is usually predominantly ionic, the lanthanide contraction often determines the differences in properties of lanthanide compounds and ions. Lanthanide compounds often have high coordination numbers between 6 and 12. see also Cerium Dysprosium Erbium Europium Gadolinium Holmium Lanthanum Lutetium Praseodymium Promethium Samarium Terbium Thulium Ytterbium. 

The concepts derived from atomic spectra have been very important in the recent progress of understanding spectroscopic properties and such chemical questions as the deviations of the oxidation state from M(III) and the conditions for metallic character of the compounds. We return to these individual properties specifically dependent on 4f in section 2, and we start with the smoothly varying properties which can be described as if the lanthanide M(III) is a sphere of electronic density gradually decreasing its radius from lanthanum to lutetium. The contributions of quantum chemistry to this, apparently simpler problem, have been much more qualitative than the specifically spectroscopic statements. 

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