Lutetium
Lutetium | ||||||||||||||||||||||||||||||||||||
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Pronunciation | /ljuːˈtiːʃiəm/ | |||||||||||||||||||||||||||||||||||
Appearance | silvery white | |||||||||||||||||||||||||||||||||||
Standard atomic weight Ar°(Lu) | ||||||||||||||||||||||||||||||||||||
Lutetium in the periodic table | ||||||||||||||||||||||||||||||||||||
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kJ/mol | ||||||||||||||||||||||||||||||||||||
Heat of vaporization | 414 kJ/mol | |||||||||||||||||||||||||||||||||||
Molar heat capacity | 26.86 J/(mol·K) | |||||||||||||||||||||||||||||||||||
Vapor pressure
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Atomic properties | ||||||||||||||||||||||||||||||||||||
Discovery | Carl Auer von Welsbach and Georges Urbain (1906) | |||||||||||||||||||||||||||||||||||
First isolation | Carl Auer von Welsbach (1906) | |||||||||||||||||||||||||||||||||||
Named by | Georges Urbain (1906) | |||||||||||||||||||||||||||||||||||
Isotopes of lutetium | ||||||||||||||||||||||||||||||||||||
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Lutetium is a
Lutetium was independently discovered in 1907 by French scientist
Lutetium is not a particularly abundant element, although it is significantly more common than
Characteristics
Physical properties
A lutetium atom has 71 electrons, arranged in the configuration [Xe] 4f145d16s2.[12] 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 the lanthanide contraction,[13] and as a result lutetium has the highest density, melting point, and hardness of the lanthanides.[14] As lutetium's 4f orbitals are highly stabilized only the 5d and 6s orbitals are involved in chemical reactions and bonding;[15][16] thus it is characterized as a d-block rather than an f-block element,[17] and on this basis some consider it not to be a lanthanide at all, but a transition metal like its lighter congeners scandium and yttrium.[18][19]
Chemical properties and compounds
Lutetium's compounds almost always contain the element in the 3+ oxidation state.[20] 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. The oxide, hydroxide, fluoride, carbonate, phosphate and oxalate are insoluble in water.[21]
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 and
Lutetium dissolves readily in weak acids[22] and dilute sulfuric 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+.[24]
- 2 Lu + 3 H2SO4 → 2 Lu3+ + 3 SO2−4 + 3 H2↑
Oxidation states
Lutetium is usually found in the +3 oxidation state, like most other lanthanides. However, it can also be in the 0, +1 and +2 states as well.
Isotopes
Lutetium occurs on the Earth in form of two isotopes: lutetium-175 and lutetium-176. Out of these two, only the former is stable, making the element monoisotopic. The latter one, lutetium-176, decays via beta decay with a half-life of 3.78×1010 years; it makes up about 2.5% of natural lutetium.[6] To date, 40
The element also has 43 known nuclear isomers, with masses of 150, 151, 153–162, and 166–180 (not every mass number corresponds to only one isomer). The most stable of them are lutetium-177m, with a half-life of 160.4 days, and lutetium-174m, with a half-life of 142 days; these are longer than the half-lives of the ground states of all radioactive lutetium isotopes except lutetium-173, 174, and 176.[6]
History
Lutetium, derived from the Latin
The International 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 names as official ones, based on the fact that the separation of lutetium from Marignac's ytterbium was first described by Urbain;[28] after Urbain's names were recognized, neoytterbium was reverted to ytterbium. An obvious issue with this decision is that Urbain was on the International Commission of Atomic Weights.[36] Until the 1950s, some German-speaking chemists called lutetium by Welsbach's name, cassiopeium; in 1949, the spelling of element 71 was changed to lutetium. The reason for this was that Welsbach's 1907 samples of lutetium had been pure, while Urbain's 1907 samples only contained traces of lutetium.[37] This later misled Urbain into thinking that he had discovered element 72, which he named celtium, which was actually very pure lutetium. The later discrediting of Urbain's work on element 72 led to a reappraisal of Welsbach's work on element 71, so that the element was renamed to cassiopeium in German-speaking countries for some time.[37] Charles James, who stayed out of the priority argument, worked on a much larger scale and possessed the largest supply of lutetium at the time.[38] Pure lutetium metal was first produced in 1953.[38]
Occurrence and production
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 earth phosphate mineral monazite (Ce,La,...)PO
4, which has concentrations of only 0.0001% of the element,[22] 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. [39] 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.[38] 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 of gold.[40][41]
Crushed minerals are treated with hot concentrated sulfuric 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 with ammonium oxalate to convert rare earths into their insoluble oxalates. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric 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 with ammonium nitrate by crystallization. Lutetium is separated by ion exchange. In this process, rare-earth ions are sorbed 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 by reduction of anhydrous LuCl3 or LuF3 by either an alkali metal or alkaline earth metal.[21]
- 2 LuCl3 + 3 Ca → 2 Lu + 3 CaCl2
Applications
Because of production difficulty and high price, lutetium has very few commercial uses, especially since it is rarer than most of the other lanthanides but is chemically not very different. However, stable lutetium can be used as
Aside from stable lutetium, its radioactive isotopes have several specific uses. The suitable half-life and decay mode made lutetium-176 used as a pure beta emitter, using lutetium which has been exposed to
Lutetium tantalate (LuTaO4) is the densest known stable white material (density 9.81 g/cm3)[56] and therefore is an ideal host for X-ray phosphors.[57][58] The only denser white material is thorium dioxide, with density of 10 g/cm3, but the thorium it contains is radioactive.
Lutetium is also a compound of several scintillating materials, which convert X-rays to visible light. It is part of LYSO, LuAg and lutetium iodide scintillators.
Lutetium (177Lu) vipivotide tetraxetan is a therapy for prostate cancer, FDA approved in 2022.[59]
Precautions
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.[22] Lutetium nitrate may be dangerous as it may explode and burn once heated. Lutetium oxide powder is toxic as well if inhaled or ingested.[22]
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.[38] 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.[38] 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.[38]
See also
References
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- 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.
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- S2CID 197766399. 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.)
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