Gadolinium atomic radius

Based on simple electrostatic theory one would predict a more or less direct relationship between the formation constants and say the atomic numbers or the ionic radii of the lanthanides, as the ionic radii varies more or less monotonically along the series and do not show (Fig. 4) any strong gadolinium break (12). However, as we have seen from the plots in Fig. 3 that the variation of the formation constants are no simple function of the atomic numbers or the ionic radii. Thus Grenthe (19) writes The experimental results proved that there was no simple variation of the measured properties with the crystallographic ionic radius - on the contrary a double series was observed. The author feels that at this point some comments on the practice of plotting the formation constants vs. the ionic radii or any function of the ionic radii (polarizability) should be made. 

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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