Scandium: discovery

Gallium [7440-55-3] atomic number 31, was discovered through a study of its spectral properties in 1875 by P. E. Lecoq de Boisbaudran and named from Gallia in honor of its discoverer s homeland. The first element to be discovered after the pubHcation of Mendeleev s Periodic Table, its discovery constituted a confirmation of the Table which was reinforced shordy after by the discoveries of scandium and germanium. 

And Maher goes on explicitly to underline the conclusions about confirmatory weight that he sees as illustrated by this episode. He claims that Mendeleev s prediction of the existence of the third of the new elements, eka-silicon (aka germanium), was initially regarded as quite unlikely to be true but then later, with the discovery of the first two new elements (gallium and scandium), confidence in the prediction of the existence of the third new element became so high that its eventual empirical confirmation was widely regarded as a matter of course. Maher writes ... 

Firstly, although we have said it several times already, it may be as well to emphasise yet again that of course we agree that the predictive successes played an important role. As we indicated earlier, Mendeleev s prediction played no part in the actual discovery of gallium, the first new element. But in the case of scandium, the second new element, its discoverer, Cleve, remarked ... 

The other direction concerns the use of immobilized transition metal catalysts in the synthesis of libraries of organic compounds of interest in therapeutic drug discovery. One such strategy uses immobilized catalysts (e.g., scandium complexes), leading to efficient library syntheses of quinolines, amino ketones, and amino acid esters.72,73... 

The discovery of gallium was followed by the discovery of scandium (Mendeleev s eka-boron) in 1879 and of germanium (eka-sili-con) in 1886. The new elements had the approximate atomic weights and properties that Mendeleev had predicted. The scientific world was astonished. It is probably safe to say that before Mendeleev s predictions were confirmed, no chemist would have believed that the properties of unknown elements could be predicted with such accuracy. 

After commenting on the discovery of gallium, scandium, and germanium (eka-aluminum, eka-boron, and eka-silicon), D. I. Mendeleev had written in 1891, I foresee some more new elements, but not with the same certitude as before. I shall give one example, and yet I do not see it quite distinctly (7). He had then proceeded to describe an undiscovered dvi tellurium with an atomic weight of about 212. Since polonium resembles tellurium and has an estimated atomic weight of about 210, it is probably the realization of Mendeleev s dvi tellurium. ... 

Examination of the Egyptian material led to a further discovery. The general Nile pattern, produced by Nile muds and the ceramics made from it, is on first glance very close to that of the Palestinian red field clay. When the plots of three clays and six sherds were matched by the scandium—iron points, cobalt, chromium, and europium also matched exactly. Thus in the Nile samples, concentrations of the five elements are highly mutually correlated. This observation then allowed detection of subtle differences between Palestinian and Egyptian materials. The... 

Mendeleeff had found himself forced to leave a number of places in his system unoccupied. He believed correctly that elements as yet unknown would find their places in these gaps. His accurate prediction of the properties of these missing elements, which he named eka-boron, eka-aluminium and eka-silicon, was brilliantly confirmed a short time later by the discovery of scandium (21), gallium (31) and germanium (32). The Inert (or Rare) Gases discovered later by Rayleigh and Ramsay could also be readily included in the system. Again, the latest, non-radioactive elements discovered, hafnium (72) [Von Hevesy and Coster, (1923)] and rhenium (75) [Nod-... 

Lanthanide elements have atomic numbers ranging from 57 to 71. With the inclusion of scandium (Sc) and yttrium (Y), a total of 17 elements are referred to as the rare earth elements. A mixture of rare earths was discovered in 1794 by J. Gadolin and ytterbium was separated from this mixture in 1878 by Mariganac, while the last rare earth element promethium (Pm) was separated by a nuclear reaction in 1974. Therefore, a period of more than 100 years separates the discovery of all the rare earth elements. In the latter part of the last century scientists started to focus on the applications of rare earth elements. Numerous interesting and important properties were found with respect to their magnetic, optical, and electronic behavior. This is the reason that many countries list all rare earth elements, except promethium (Pm), as strategic materials. Rare earth coordination chemistry, therefore, developed quickly as a result of this increased activity. 

Further confirmation came when Lars Nilson (1840-1899) announced the discovery of scandium (after Scandinavia), in 1879, which matched Mendeleev s eka-boron, and Clemens Winkler s (1838-1904) announcement of the discovery of germanium (after his home country of Germany) in 1886 which matched eka-silicon. Mendeleev s theoretical position triumphed, and his table began to be accepted as a genuine insight into the order of the material world. 

Cdtium was isolated from the soluble end of a series from gadolinite by fractional crystallization of the nitrates in nitric add. Its compounds have properties intermediate between those of scandium and lutecium. Its atomic weight has not been determined, but the atomic number 72 has been assigned to this element. The discovery of hafnium, a close relative of... 

Even before the discovery of gallium, scandium, and germanium, the spectroscope had been qsed in a spectacular way to identify another unknown element. 

The most famous of Mendeleev s predictions involved eka-boron (scandium), eka-aluminium (gallium), and eka-silicon (germanium). For example, for eka-silicon he predicted its atomic weight, its density, the compounds it would form, and details about their physical properties. When thirteen years later germanium was discovered and it was determined that Mendeleev s predictions had been correct, scientists began to recognize the importance of the Periodic Table, and its discovery was quite naturally associated with Mendeleev, who encouraged this association. 

Since its discovery, scandium has been found only in several rare minerals. It is found in highest concentration in the Norwegian mineral thortveitite (35-40% scandium). Its abundance in Earth s crust is a point of conjecture it is generally agreed that scandium occurs in greater abundance in the Sun and certain stars. 

In due course these elements were discovered and christened scandium, gallium and germanium respectively. They were found to possess properties remarkably close to those predicted by MendeteefF, and their discovery removed all lingering doubts as to the importance of the Periodic Law. 

Multi-component reaction for the preparation of a variety of compounds in a single step is a powerful tool in combinatorial chemistry and drug discovery. Reaction of cyclohexyliso-nitrile and isobutyraldehyde in methanol in the presence of dimethy lamine hydrochloride as a weak acid catalyst produces A -cyclohexyl-a-dimethylaminoisovaleramide and the corresponding a-hydroxy compound [29] (Scheme 3.17). a-Aminoamidine is obtained as a sole product when dimethylamine is added as a nucleophile. Keung et al. [30] optimized the reaction conditions using various metal catalysts. Scandium (111) triflate was found to be the best catalyst and tolerant to a wide variety of amine and aldehyde units. 

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