Lutetium

Lutetium is a chemical element, with atomic number 71, whose chemical symbol is Lu. Despite being one of the d-block elements, it is frequently included among the lanthanides (rare earths), since it shares many properties with them. Of all of them, it is the most difficult element to isolate, which justifies its high cost and the relatively few uses that have been found for it.

Lutetium is not a particularly abundant element, although it is significantly more common than silver in the Earth's crust. It has few specific uses. Lutetium-176 is a relatively abundant (2.5%) radioactive isotope with a half-life of about 38 billion years, used to age minerals and meteorites. Lutetium usually occurs in association with the element yttrium and is sometimes used in metal alloys and as a catalyst in various chemical reactions. ¹⁷⁷Lu-DOTA-TATE is used in radionuclide therapy (see Nuclear Medicine) to treat neuroendocrine tumors. Lutetium has the highest Brinell hardness of all the lanthanides, at 890–1,300 MPa.

Features

Lutetium is a trivalent metal, silvery-white in color, resistant to corrosion and, in the presence of air, relatively stable. Of all the rare earths it is the heaviest and hardest element.

Applications

Due to the difficulty of production and its high price, lutetium has very few commercial uses, mainly because it is rarer than most other lanthanides, but chemically it is not very different

Stable lutetium can be used as a catalyst in the cracking of petroleum in refineries, and in various chemical processes, such as alkylation, hydrogenation, and polymerization. Radioisotopes of lutetium are also being investigated to be applied in nuclear medicine in therapeutic treatments.

Lutetium aluminum garnet (Al
5Lu
3O
12) has been proposed for use as a high refractive index lens material. immersion lithography. In addition, a small amount of lutetium is added as a dopant to gallium gadolinium garnet, which is used in magnetic bubble memory devices. Cerium-doped lutetium oxyorthosilicate is currently the preferred compound for positron emission tomography (PET) detectors. Lutetium aluminum garnet (LuAG) is used as a phosphor in light-emitting diode bulbs.

In addition to stable lutetium, its radioactive isotopes have several specific uses. The suitable half-life and mode of decay led to lutetium-176 being used as a pure beta emitter, using lutetium that has been exposed to neutron activation, and in lutetium-hafnium dating to date meteorites. The isotope synthetic lutetium-177 bound to octreotate (a somatostatin analogue), is used experimentally in targeted radionuclide therapy for neuroendocrine tumors. Indeed, lutetium-177 is increasingly being used as a radionuclide in neuroendocrine therapy of tumors and palliation of bone pain.

Research indicates that lutetium ion atomic clocks could provide greater precision than any existing atomic clock.

Lutetium tantalate (LuTaO₄) is the densest known stable white material (density 9.81 g/cm³) and is therefore an ideal receptor of X-ray phosphors. The only denser white material is thorium dioxide, which has a density of 10 g/cm³, but the thorium it contains is radioactive.

History

Lutetium, from the Latin Lutetia (first name of Paris), was discovered independently in 1907 by the French scientist Georges Urbain, the Austrian mineralogist Baron Carol Auer von Welsbach, and the American chemist Charles James.. They found it as an impurity of the metal ytterbium, which the Swiss chemist Jean Charles Galissard de Marignac and most of his colleagues had considered a pure mineral. Scientists proposed different names for the elements: Urbain chose neoytterbium and lutetium, while Welsbach chose aldebaranium and cassiopeium (for Aldebaran and Cassiopeia). Both articles accused the other of publishing results based on the author's.

The International Commission on Atomic Weights, then responsible for attributing new element names, resolved the dispute in 1909 by granting priority to Urbain and adopting their names as official, on the grounds that the separation from Marignac ytterbium lutetium was first described by Urbain; after the Urbain names were recognized, the neoiterbic was reverted to ytterbium. Until the 1950s, some German-speaking chemists called lutetium by the Welsbach name, cassiopeium; in 1949, the spelling of element 71 was changed to lutetium. The reason was that Welsbach's 1907 lutetium samples had been pure, whereas Urbain's 1907 samples contained only trace amounts of lutetium. This led Urbain to believe that he had discovered element 72, which he named celtium, which was actually it was very pure lutetium. The subsequent discredit of Urbain's work on element 72 led to a reappraisal of Welsbach's work on element 71, so that the element came to be called cassiopean in German-speaking countries for some time. Charles James, who stayed out of the priority discussion, worked on a much larger scale and possessed the largest supply of lutetium at the time. Pure metallic lutetium was first produced in 1953.

Abundance

In nature it occurs with most other rare earths, but never alone, native. Of all the elements present in nature, it is the least abundant. The main commercially exploitable lutetium ore is monazite (Ce, La, etc.)PO₄, which contains 0.003% Lu.

Until the end of the XX century d. C. it was not possible to obtain the pure metal, since it is extremely difficult to prepare. The procedure used is the ion exchange (reduction) of anhydrous LuCl₃ or LuF₃ with alkali metal or alkaline earth metal.

Isotopes

There is a stable isotope of lutetium, Lu-175, with a natural abundance of 97.41%. 33 radioisotopes have been identified. The most stable are Lu-176, with a half-life of 3.78×10¹⁰ years and natural abundance of 2.59%, Lu-174, with a half-life of 3.31 years, and the Lu-173, 1.37 years. The half-lifes of the rest of its radioactive isotopes are less than nine days; most, less than half an hour. In addition, there are 18 metastates, of which the most stable are: Lum-177, Lum-174 and Lum-178, whose respective half-lifes are 160.4 days, 142 days and 23.1 minutes.

The atomic masses of the lutetium isotopes vary between 149.973 amu, for Lu-150, and 183.962, for Lu-184. The main decay modality of isotopes lighter than the stable one is by electron capture (ε), (with some cases of α decay), from which ytterbium isotopes are generated. Isotopes heavier than stable decay by β emission, the result of which is hafnium isotopes.

Precautions

Like the rest of the rare earths, the toxicity of this metal is assumed to be low. However, both lutetium and -especially- its compounds must be handled with the utmost caution. Although it has no biological function in the human body, it is believed to stimulate metabolism.