Rare earth oxide elements cerium group

Symbol Nd atomic number 60 atomic weight 144.24 a rare earth lanthanide element a hght rare earth metal of cerium group an inner transition metal characterized by partially filled 4/ subshell electron configuration [Xe]4/35di6s2 most common valence state -i-3 other oxidation state +2 standard electrode potential, Nd + -i- 3e -2.323 V atomic radius 1.821 A (for CN 12) ionic radius, Nd + 0.995A atomic volume 20.60 cc/mol ionization potential 6.31 eV seven stable isotopes Nd-142 (27.13%), Nd-143 (12.20%), Nd-144 (23.87%), Nd-145 (8.29%), Nd-146 (17.18%), Nd-148 (5.72%), Nd-150 (5.60%) twenty-three radioisotopes are known in the mass range 127-141, 147, 149, 151-156. 

Rare Earths. Oxides of the rare earth elements of Group III in the Periodic System. Those used in ceramics are the oxides of lanthanum, cerium, PRASEODYMIUM, NEODYMIUM, and YTTRIUM (q.V.). 

The accommodation of cerium went smoothly as Mendeleev had correctly determined its atomic weight and oxide formulae. According to the dualism of cerium, this rare-earth element exhibited two oxidation states (+III and +IV), making its placement in the fourth group very natural. As Mendeleev reasoned in his article On the Placement of Cerium in the Periodic System of Elements ... 

Thus, Mosander s activities led to the originally two-element division into a six-element division. The cerium compounds are yellow at the higher oxidation level and colourless at the lower oxidation level, lanthanum compounds are white, didymium compounds are red, yttrium and erbium compounds are white, terbium compounds are pink. Chemists existed, of course, who disputed the existence of these elements. Unequivocal identification of elements was, however, possible in later times only. In the period in question, the main characteristics on the basis of which a substance could be qualified as a new element were separability, colour, crystal shape and reactivity. Even atomic mass determinations were largely uncertain, particularly in the group of the rare earth elements, it will be seen in the... 

In the comprehensive studies of the radioactive species produced in the fission of uranium it has been found that over thirty are members of the rare earth family (isotopes of yttrium and the group lanthanum through europium). The chemical and physical identification of these was an important part of the research program of the Manhattan Project. Standard oxidative separations and fractional precipitations and the use of radiochemical methods based on chain relations served to distinguish the activities of yttrium, lanthanum, cerium, and some of praseodymium, and those of samarium and europium. The characterization of the sequence praseodymium, neodymium, and element 61 presented very difficult problems that were solved only with the intensification of ion exchange methods originally developed by Boyd and co-workers and applied to the rare earth field by Cohn and co-workers. (Marinsky et al. 1947)... 

Ever since his arrival in Florence, Rolla conducted research on the group of rare earths with the specific intention of isolating the element possessing atomic number 61. He smdied new methods of fractional crystallization, the method of choice for separating rare earth elements. He worked first with small, then with immense quantities of material so that in the 1930s the Instimte possessed, as its Director declared with great pride, the richest and purest collection of cerium oxides in the world [147]. ... 

A group of fourteen elements starting from cerium (58) to lutecium (71) constitute the lanthanide series. These elements were also characterized as Rare earths since origiuedly they were obtained as earths (oxides) from relatively rare minerals. These elements from thorium (Thgo) to lawrencium (LW103), again a group of fourteen elements, form the actinide series. 

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