Samarium atomic radius

One effect of lanthanide contraction is that the radius of trivalent yttrium ion (Y +) is measured to be between that of Ho + and Er +, and the atomic radius of yttrium is between neodymium and samarium. This results in the chemical properties of yttrium being very similar to those of lanthanide elements. Yttrium is often found with lanthanide elements in natural minerals. The chemical properties of yttrium may be similar to the lighter or the heavier lanthanide elements in different systems and this depends on the level of covalent character of the chemical bonds in those systems. 

Table 9.1. The theoretical variation off and f" with (sind)IX for a K shell (cobalt) and an L shell (samarium) for Cu K wave-length. The K shell radius is less than the L shell so that fall off with (sind)IX is less significant. In turn, the fall off off0 is pro rata much greater because of the large size of the atom compared with the core shell radii. Values off and f" for (sind)IX = 0 are from Dauben and Templeton (1955) the corrections for other values of sindIX are derived from Berghuis et al (1955) and Veenendaal et al (1959) (extracted from International Tables of Crystallography III 213-16) with permission. Units off, f" and f0 are in e. ...

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. 

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