الفهرس | Only 14 pages are availabe for public view |
Abstract The larger group of elements in the sexth periodic table known as the rare earths or lanthanides includes 15 elements: 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 (rlJ) and lutetium (Lu). In nature the lantb.anides occur with yttrium (Y) which has a very si8ilar chemical properties and so both are often discussed togother. Since their discovery in 1794 in the mineral ytterbite (later renamed gadolinite), the lanthanides has attra~ted the inteEest of many investigators for over 138 years. Many chemical, magnetic and spectroscopic data on the electronic structure Gf the lanthani~es in the atomic and ionic states have been reported1 •2 •3. It is firmely established that the unusual change in the properties within the lanthanides fgmily is due to the order of :fillinG of the electron shell. Because of the peculair nature of the wave function of the lanthanides, the filling of the 4f shells is energetically more advantageous than the filling .of the eutermost 5d and 6p shells |