Lutetium was independently discovered in 1907 by French scientistGeorges Urbain, Austrian mineralogistBaronCarl Auer von Welsbach, and American chemistCharles James.[10] All of these researchers found lutetium as an impurity inytterbium. The dispute on the priority of the discovery occurred shortly after, with Urbain and Welsbach accusing each other of publishing results influenced by the published research of the other; the naming honor went to Urbain, as he had published his results earlier. He chose the namelutecium for the new element, but in 1949 the spelling was changed tolutetium. In 1909, the priority was finally granted to Urbain and his names were adopted as official ones; however, the namecassiopeium (or latercassiopium) for element 71 proposed by Welsbach was used by many German scientists until the 1950s.[11]
Lutetium is not a particularly abundant element, although it is significantly more common thansilver 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 todetermine the age of minerals andmeteorites. Lutetium usually occurs in association with the elementyttrium[12] and is sometimes used in metalalloys and as acatalyst in various chemical reactions.177Lu-DOTA-TATE is used forradionuclide therapy (seeNuclear medicine) on neuroendocrine tumours. Lutetium has the highestBrinell hardness of any lanthanide, at 890–1300MPa.[13]
A lutetium atom has 71 electrons, arranged in theconfiguration [Xe] 4f145d16s2.[14] Lutetium is generally encountered in the +3 oxidation state, having lost its two outermost 6s and the single 5d-electron. The lutetium atom is the smallest among the lanthanide atoms, due to thelanthanide contraction,[15] and as a result lutetium has the highest density, melting point, and hardness of the lanthanides.[16] As lutetium's 4f orbitals are highly stabilized only the 5d and 6s orbitals are involved in chemical reactions and bonding;[17][18] thus it is characterized as a d-block rather than an f-block element,[19] and on this basis some consider it not to be a lanthanide at all, but atransition metal like its lighter congenersscandium andyttrium.[20][21]
Lutetium's compounds almost always contain the element in the +3 oxidation state.[22] Aqueous solutions of most lutetium salts are colorless and form white crystalline solids upon drying, with the common exception of the iodide, which is brown. The soluble salts, such as nitrate, sulfate and acetate form hydrates upon crystallization. Theoxide, hydroxide, fluoride, carbonate, phosphate andoxalate are insoluble in water.[23]
Lutetium metal is slightly unstable in air at standard conditions, but it burns readily at 150 °C to form lutetium oxide. The resulting compound is known to absorb water andcarbon dioxide, and it may be used to remove vapors of these compounds from closed atmospheres.[24] Similar observations are made during reaction between lutetium and water (slow when cold and fast when hot); lutetium hydroxide is formed in the reaction.[25] Lutetium metal is known to react with the four lightest halogens to formtrihalides; except the fluoride they are soluble in water.[citation needed]
Lutetium dissolves readily in weak acids[24] and dilutesulfuric acid to form solutions containing the colorless lutetium ions, which are coordinated by between seven and nine water molecules, the average being[Lu(H2O)8.2]3+.[26]
Lutetium occurs on the Earth in two isotopes: lutetium-175 and lutetium-176. Out of these two, only the former is stable, making the elementmonoisotopic. The latter one, lutetium-176, decays viabeta decay with ahalf-life of3.70×1010 years; it makes up about 2.5% of natural lutetium.[8]
To date, 40synthetic radioisotopes of the element have been characterized, ranging inmass number from 149 to 188; the most stable such isotopes are lutetium-174 with a half-life of 3.31 years, and lutetium-173 with a half-life of 1.37 years. All of the remainingradioactive isotopes have half-lives that are less than 9 days, and the majority of these have half-lives that are less than half an hour. Isotopes lighter than the stable lutetium-175 decay viaelectron capture (to produce isotopes ofytterbium), with somealpha andpositron emission; the heavier isotopes decay primarily via beta decay, producinghafnium isotopes.[8] Experiments at theFacility for Rare Isotope Beams have reported lutetium-190 in fragments of platinum-198 colliding with a carbon target.[27]
The element also has 43 knownnuclear isomers, of which the most stable of them are lutetium-177m3, with a half-life of 160.4 days, and lutetium-174m with a half-life of 142 days; longer than the ground states of all lutetium isotopes except 173-176.[8]
Three scientists were involved in the discovery of lutetium:[28] French scientistGeorges Urbain,[29] Austrian mineralogist BaronCarl Auer von Welsbach,[30] and American chemist Charles James.[31][32] They found lutetium as an impurity inytterbia, which was thought by Swiss chemistJean Charles Galissard de Marignac to consist entirely ofytterbium. Of the three, Urbain was the first to publish, followed by Welsbach; James was about to publish when he learned of Urbain's work, and thereafter gave up his claim and did not publish.[33] Despite staying out of the priority argument, James worked on a much larger scale and possessed the largest supply of lutetium at the time.[34]
Urbain and Welsbach proposed different names. Urbain choseneoytterbium for ytterbium andlutecium for the new element.[35] Welsbach chosealdebaranium andcassiopeium (afterAldebaran andCassiopeia). Both authors accused the other man of publishing results based on their work.[36][37]TheInternational Commission on Atomic Weights, which was then responsible for the attribution of new element names, settled the dispute in 1909 by granting priority to Urbain and adopting his choice for a name, one derived from the LatinLutetia (Paris). This decision was based on the fact that the separation of lutetium from Marignac's ytterbium was first described by Urbain.[29] Welsbach had achieved the separation before Urbain, but Urbain had published 44 days earlier. Since Urbain was on the commission which made the decision, its objectivity could be questioned and furthermore Welsbach protested that Urbain's spectral evidence was weak and argued that his rival's lutetium was very impure, but to no avail.[33] After Urbain's names were recognized, neoytterbium was reverted to ytterbium.[38]
The controversy died down after 1910, only to be reignited with the discovery of element 72. Urbain claimed in 1911 to have discovered a new rare earth namedceltium and identified it as element 72. However,Niels Bohr had demonstrated from his quantum theory that element 72 had to be agroup 4 element and not a rare earth, and based on an idea byFritz Paneth, Bohr's friendGeorge de Hevesy worked withDirk Coster to search for it inzirconium minerals. This they succeeded in doing, discoveringhafnium in 1923. This discovery announcement, being in direct conflict with Urbain's celtium, ignited a controversy on element 72 throughout the 1920s; the resulting investigations on the nature of Urbain's celtium, since it was not the same as hafnium, reopened the case on element 71. The physicistsHans M. Hansen andSven Werner, at Bohr's Copenhagen institute, found in 1923 that Welsbach's 1907 samples of cassiopeium had been pure element 71, while Urbain's 1907 lutecium samples only contained traces of element 71 and his 1911 samples identified asceltium were actually pure element 71 – confirming Welsbach's criticism.[39][33] The Copenhagen physicists then started a campaign to re-award priority for element 71 to Welsbach and replace the name lutetium with cassiopeium, writing to Welsbach in 1923 of their intentions. This campaign encountered success in the physics literature, but in spite of strong German and Scandinavian support for cassiopeium, lutetium remained embedded in most of the chemical literature, with the International Commission on Atomic Weights in 1930 accepting that element 72 was hafnium but using lutetium for element 71.[33]
In 1949, it was decided by theInternational Union of Pure and Applied Chemistry to recommend the name lutetium, since cassiopeium by then was only used in German and sometimes Dutch, and it was a difficult name to adapt to other languages; it was nonetheless clarified that this was not intended as a statement on priority. Urbain's spellinglutecium was changed tolutetium, in order to derive the name from LatinLutetia instead of FrenchLutèce.[40] Pure lutetium metal was first produced in 1953.[34]
Found with almost all other rare-earth metals but never by itself, lutetium is very difficult to separate from other elements. Its principal commercial source is as a by-product from the processing of the rare earthphosphate mineralmonazite (Ce,La,...)PO 4, which has concentrations of only 0.0001% of the element,[24] not much higher than the abundance of lutetium in the Earth crust of about 0.5 mg/kg. No lutetium-dominant minerals are currently known.[41] The main mining areas are China, United States, Brazil, India, Sri Lanka and Australia. The world production of lutetium (in the form of oxide) is about 10 tonnes per year.[34] Pure lutetium metal is very difficult to prepare. It is one of the rarest and most expensive of the rare earth metals with the price about US$10,000 per kilogram, or about one-fourth that ofgold.[42][43]
Crushed minerals are treated with hot concentratedsulfuric acid to produce water-soluble sulfates of rare earths.Thorium precipitates out of solution as hydroxide and is removed. After that the solution is treated withammonium oxalate to convert rare earths into their insoluble oxalates. The oxalates are converted to oxides by annealing. The oxides are dissolved innitric acid that excludes one of the main components,cerium, whose oxide is insoluble in HNO3. Several rare earth metals, including lutetium, are separated as a double salt withammonium nitrate by crystallization. Lutetium is separated byion exchange. In this process, rare-earth ions areadsorbed onto suitable ion-exchange resin by exchange with hydrogen, ammonium or cupric ions present in the resin. Lutetium salts are then selectively washed out by suitable complexing agent. Lutetium metal is then obtained byreduction of anhydrous LuCl3 or LuF3 by either analkali metal oralkaline earth metal.[23]
2 LuCl3 + 3 Ca → 2 Lu + 3 CaCl2
177Lu is produced byneutron activation of176Lu or by indirectly by neutron activation of176Yb followed bybeta decay. The 6.693-day half-life allows transport from the production reactor to the point of use without significant loss in activity.[44]
Lutetium tantalate (LuTaO4) is the densest known stable white material (density 9.81 g/cm3)[52] and therefore is an ideal host for X-ray phosphors.[53][54] The only denser white material isthorium dioxide, with density of 10 g/cm3, but the thorium it contains is radioactive.
The isotope177Lu emits low-energy beta particles and gamma rays and has a half-life around 7 days, positive characteristics for commercial applications, especially in therapeutic nuclear medicine.[44]The synthetic isotopelutetium-177 bound to octreotate (asomatostatin analogue), is used experimentally in targetedradionuclide therapy forneuroendocrine tumors.[57] Lutetium-177 is used as a radionuclide in neuroendocrine tumor therapy and bone pain palliation.[58][59]
Like other rare-earth metals, lutetium is regarded as having a low degree of toxicity, but its compounds should be handled with care nonetheless: for example, lutetium fluoride inhalation is dangerous and the compound irritates skin.[24] Lutetium nitrate may be dangerous as it may explode and burn once heated. Lutetium oxide powder is toxic as well if inhaled or ingested.[24]
Similarly to the other rare-earth metals, lutetium has no known biological role, but it is found even in humans, concentrating in bones, and to a lesser extent in the liver and kidneys.[34] Lutetium salts are known to occur together with other lanthanide salts in nature; the element is the least abundant in the human body of all lanthanides.[34] Human diets have not been monitored for lutetium content, so it is not known how much the average human takes in, but estimations show the amount is only about several micrograms per year, all coming from tiny amounts absorbed by plants. Soluble lutetium salts are mildly toxic, but insoluble ones are not.[34]
^abArblaster, John W. (2018).Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International.ISBN978-1-62708-155-9.
^Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, seeCloke, F. Geoffrey N. (1993). "Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides".Chem. Soc. Rev.22:17–24.doi:10.1039/CS9932200017. andArnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (2003-12-15). "Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation".Journal of Organometallic Chemistry.688 (1–2):49–55.doi:10.1016/j.jorganchem.2003.08.028.
^All thelanthanides, except Pm, in the +2 oxidation state have been observed in organometallic molecular complexes, seeLanthanides Topple Assumptions andMeyer, G. (2014). "All the Lanthanides Do It and Even Uranium Does Oxidation State +2".Angewandte Chemie International Edition.53 (14):3550–51.doi:10.1002/anie.201311325.PMID24616202.. Additionally, all thelanthanides (La–Lu) form dihydrides (LnH2), dicarbides (LnC2), monosulfides (LnS), monoselenides (LnSe), and monotellurides (LnTe), but for most elements these compounds have Ln3+ ions with electrons delocalized into conduction bands, e. g. Ln3+(H−)2(e−).
^Krinsky, Jamin L.; Minasian, Stefan G.; Arnold, John (2010-12-08). "Covalent Lanthanide Chemistry Near the Limit of Weak Bonding: Observation of (CpSiMe3)3Ce−ECp* and a Comprehensive Density Functional Theory Analysis of Cp3Ln−ECp (E = Al, Ga)".Inorganic Chemistry.50 (1). American Chemical Society (ACS):345–357.doi:10.1021/ic102028d.ISSN0020-1669.PMID21141834.
^Welsbach, Carl A. von (1908)."Die Zerlegung des Ytterbiums in seine Elemente" [Resolution of ytterbium into its elements].Monatshefte für Chemie.29 (2):181–225, 191.doi:10.1007/BF01558944.S2CID197766399. On page 191, Welsbach suggested names for the two new elements:"Ich beantrage für das an das Thulium, beziehungsweise Erbium sich anschließende, in dem vorstehenden Teile dieser Abhandlung mit Yb II bezeichnete Element die Benennung: Aldebaranium mit dem Zeichen Ad — und für das zweite, in dieser Arbeit mit Yb I bezeichnete Element, das letzte in der Reihe der seltenen Erden, die Benennung: Cassiopeïum mit dem Zeichen Cp." (I request for the element that is attached to thulium or erbium and that was denoted by Yb II in the above part of this paper, the designation "Aldebaranium" with the symbol Ad — and for the element that was denoted in this work by Yb I, the last in the series of the rare earths, the designation "Cassiopeïum" with the symbol Cp.)
^James, C. (1907)."A new method for the separation of the yttrium earths".Journal of the American Chemical Society.29 (4):495–499.Bibcode:1907JAChS..29..495J.doi:10.1021/ja01958a010. In a footnote on page 498, James mentions that Carl Auer von Welsbach had announced " ... the presence of a new element Er, γ, which is undoubtedly the same as here noted, ... ." The article to which James refers is: C. Auer von Welsbach (1907)"Über die Elemente der Yttergruppe, (I. Teil)" (On the elements of the ytterbium group (1st part)),Monatshefte für Chemie und verwandte Teile anderer Wissenschaften (Monthly Journal for Chemistry and Related Fields of Other Sciences),27 : 935-946.
^abcdKragh, Helge (1996). "Chapter 5. Elements No. 70, 71 and 72: Discoveries and Controversies". In Evans, C. H. (ed.).Episodes from the History of the Rare Earth Elements. Kluwer Academic Publishers. pp. 67–90.ISBN978-94-010-6614-3.
^Castor, Stephen B.; Hedrick, James B. (2006)."Rare Earth Elements"(PDF). In Jessica Elzea Kogel, Nikhil C. Trivedi and James M. Barker (ed.).Industrial Minerals and Rocks. Society for Mining, Metallurgy and Exploration. pp. 769–792. Archived from the original on 2009-10-07.{{cite book}}: CS1 maint: bot: original URL status unknown (link)
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^Balter, H.; Trindade, V.; Terán, M.; Gaudiano, J.; Ferrando, R.; Paolino, A.; Rodriguez, G.; Hermida, J.; De Marco, E.; Oliver, P. (2015). "177Lu-Labeled Agents for Neuroendocrine Tumor Therapy and Bone Pain Palliation in Uruguay".Current Radiopharmaceuticals.9 (1):85–93.doi:10.2174/1874471008666150313112620.PMID25771367.
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