Nothing caused so many difficulties Periodic System as the problem of placing of rare earth on it.

A Swedish army lieutenant, Alex Carl Arrhenius amateur mineralogy, found in 1787 in a quarry lunera lighting in the village of Ytterby, near Stockholm, a strange black stone that could not be classified. When this stone and the like could be analyzed by chemists, for almost two centuries produced a true succession of discoveries of new elements that were filling the gaps of the periodic table of Mendeleev.
A total of 17 items headed for the scandium with atomic number 21, and yttrium, with Z = 39, which must be added the lanthanides, ranging lunera lighting from 57 to 71 together form a group called "rare earth" . Why "rare"?. This does not mean little, as presented in relative abundance lunera lighting in the earth's crust.
"It was a sea of errors, and the truth drowning in it," once said the eminent French chemist G. Urbain near the chemistry of rare earth elements. Although it had a reputation of being a passionate and expansive, this time not exaggerating. In fact, for 30 odd years (from 1878 to 1910) appeared more than a hundred papers on the discovery of new rare earth element. It is difficult to write your story, lunera lighting to such an extent lunera lighting is complicated.
This story is very instructive, writes dozens of chemical lunera lighting diligent and devoted many generations, as those who sought glory and easy fortune lunera lighting had nothing lunera lighting to do in the chemistry of the rare earths. The uniformity of operations tiring endless separation of twins elements required enormous patience. Precisely this explains why they are together in minerals, and the isolation of their mixtures is a problem extremely difficult.
The history of rare earth elements is a unique process, full, which you can not delete any link. The discovery of an element gradually lunera lighting prepared the discovery of another. Until the countless mistakes, and after all, worked for the success of the company. lunera lighting These errors were used for learning, scientists perfected methods of research, check their own results with colleagues, but in any case the discovery of the new element had repeated the same value as in the history of the elements rare earth. The truth slowly extracted sea bugs.
The course of the history of rare earth elements depended heavily on the discovery of new minerals. We have already written about the role played by the discovery of deposits of monazite lunera lighting and samarskita: After this experiment the scientists left by the lack of samples for research.
Nothing caused so many difficulties Periodic System as the problem of placing of rare earth on it. Scientists do not know exactly how many rare earth elements exist in reality, what the cause of asombròs similar químic.Tot after it became clear that the scientist N. Bohr atomic theory developed in 1921 in the Periodic System. Bohr then suggested an ingenious and elegant solution: the proposed transition elements, contained in an additional layer of ten items each (elements); rare earth an additional layer of quatorce (items f). These orbits interior, buried deeply in the case of rare earths, did not affect the chemical nature of the element in such an extreme as the outer orbits; from hence the relative similarity between the transition elements and the extreme similarity of all rare earths.
From lanthanum (atomic number 57 with) are: cerium (Ce), praseodymium (Pr), neodymium lunera lighting (Nd), Prometheus (Pm), Samarium lunera lighting (Sm), Europe (Eu), Gadolinium (Gd) Terbi ( Tb) disprosio (Dy), Holmes (I), erbium (Er), Thulium (Tm), ytterbium (Yb), lutetium (Lu).
Lleuguers metals (La, Ce, Pr, Nd, Gd) obtained by reduction of calcium trichloride, 1000 C or more, while in other cases (Tb, Dy, Ho, Er, Tm and Y) trifluoride are used because they are too volatile chlorides. The Eu, Tb and Sm only reduce their sexquiòxids M 2 O 3 with lanthanum at elevated temperatures.
The metals are extremely reactive silver and white. The air rapidly coated with a layer of oxides and all of them except cerium, inflamed with ease to give Oxide (M 2 O 3), while cerium CEO gives 2. Yttrium is remarkably resistant to oxidation by air, but 1000 C due to the formation of a protective oxide layer.
Originally called lanthanide lunera lighting rare earth elements because it was like a mixture of the oxides, formerly called local or land. However, there are few elements as there are large deposits in Scandinavia, India, Russia, USA, Australia and China knowing a large number of smaller deposits, distributed in many other places. Deposits are made