Thulium is achemical element; it hassymbolTm andatomic number 69. It is the thirteenth element in thelanthanide series ofmetals. It is the second-least abundant lanthanide in the Earth's crust, after radioactively unstablepromethium. It is an easily workable metal with a bright silvery-gray luster. It is fairly soft and slowlytarnishes in air. Despite its high price and rarity, thulium is used as adopant insolid-state lasers. It has no significant biological role and is not particularly toxic. Artificial radioactiveisotopes of thulium are used asradiation sources in some portableX-ray devices.
In 1879, the Swedish chemistPer Teodor Cleve separated two previously unknown components, which he calledholmia andthulia, from therare-earth mineralerbia; these were the oxides ofholmium and thulium, respectively. His example of thulium oxide contained impurities of ytterbium oxide. A relatively pure sample of thulium oxide was first obtained in 1911. The metal itself was first obtained in 1936 byWilhelm Klemm and Heinrich Bommer.[9]
Like the other lanthanides, its most commonoxidation state is +3, seen in its oxide, halides and other compounds. Inaqueous solution, like compounds of other late lanthanides, soluble thulium compounds formcoordination complexes with nine water molecules.
Pure thulium metal has a bright, silvery luster, which tarnishes on exposure to air. The metal can be cut with a knife,[10] as it has aMohs hardness of 2 to 3; it is malleable and ductile.[11] Thulium isferromagnetic below 32K,antiferromagnetic between 32 and 56K, andparamagnetic above 56K.[12]
Thulium reacts with various metallic and non-metallic elements forming a range of binary compounds, includingTmN,TmS,TmC2,Tm2C3,TmH2,TmH3,TmSi2,TmGe3,TmB4,TmB6 andTmB12.[citation needed] Like most lanthanides, the +3 state is most common and is the only state observed in thulium solutions.[16] Thulium exists as aTm3+ ion in solution. In this state, the thulium ion is surrounded by nine molecules of water.[10]Tm3+ ions exhibit a bright blue luminescence.[10] Because it occurs late in theseries, the +2 oxidation state can also exist, stabilized by the nearly full 4felectron shell, but occurs only in solids.[citation needed]
Thulium's only known oxide isTm2O3. This oxide is sometimes called "thulia".[17] Reddish-purple thulium(II) compounds can be made by thereduction of thulium(III) compounds. Examples of thulium(II) compounds include the halides (except the fluoride). Some hydrated thulium compounds, such asTmCl3·7H2O andTm2(C2O4)3·6H2O are green or greenish-white.[18] Thulium dichloride reacts very vigorously withwater. This reaction results inhydrogen gas andTm(OH)3 exhibiting a fading reddish color.[citation needed] Combination of thulium andchalcogens results in thuliumchalcogenides.[19]
Thulium reacts withhydrogen chloride to produce hydrogen gas and thulium chloride. Withnitric acid it yields thulium nitrate,Tm(NO3)3.[20]
Natural thulium consists of the single stable isotope thulium-169 (it is predicted to undergoalpha decay toholmium-165 with a very long half-life.[10][21]). Known isotopes of thulium range from144Tm to183Tm.[8][22]
The primarydecay mode before the stable isotope,169Tm, iselectron capture toerbium isotopes, and the primary mode after isbeta emission toytterbium isotopes. The longest-lived radioisotopes are thulium-171, which has ahalf-life of 1.92 years, andthulium-170, which has a half-life of 128.6 days. Most other isotopes have half-lives under 10 minutes.[8]
Per Teodor Cleve, the scientist who discovered thulium as well asholmium.
Thulium wasdiscovered by Swedish chemistPer Teodor Cleve in 1879 by looking for impurities in theoxides of other rare earth elements. This was the same methodCarl Gustaf Mosander earlier used to discover some other rare earth elements.[23] Cleve started by removing all of the known contaminants oferbia (Er2O3). Upon additional processing, he obtained two new substances; one brown and one green. The brown substance was the oxide of the elementholmium and was named holmia by Cleve, and the green substance was the oxide of an unknown element. Cleve named the oxidethulia and its element thulium afterThule, anAncient Greek place name associated with Scandinavia orIceland. Thulium's atomic symbol was initially Tu, but later[when?] changed to Tm.[why?][10][24][25][26][27][28][29]
Thulium was so rare that none of the early workers had enough of it to purify sufficiently to actually see the green color; they had to be content withspectroscopically observing the strengthening of the two characteristic absorption bands, as erbium was progressively removed. The first researcher to obtain nearly pure thulium wasCharles James, a British expatriate working on a large scale atNew Hampshire College inDurham, USA. In 1911 he reported his results, having used his discovered method of bromate fractional crystallization to do the purification. He famously needed 15,000 purification operations to establish that the material was homogeneous.[30]
High-purity thulium oxide was first offered commercially in the late 1950s, as a result of the adoption ofion-exchange separation technology. Lindsay Chemical Division of American Potash & Chemical Corporation offered it in grades of 99% and 99.9% purity. The price per kilogram oscillated between US$4,600 and $13,300 in the period from 1959 to 1998 for 99.9% purity, and it was the second highest for the lanthanides behindlutetium.[31][32]
The element is never found in nature in pure form, but it is found in small quantities inminerals with other rare earths. Thulium is often found with minerals containingyttrium andgadolinium. In particular, thulium occurs in the mineralgadolinite.[33] Like many otherlanthanides, thulium also occurs in the mineralsmonazite,xenotime, andeuxenite. Thulium has not been found in prevalence over the other rare earths in any mineral yet.[34] Itsabundance in the Earth's crust is 0.5 mg/kg by weight.[35]
Thulium makes up approximately 0.5 parts per million ofsoil, although this value can range from 0.4 to 0.8 parts per million. Thulium makes up 250 parts per quadrillion ofseawater.[10] In theSolar System, thulium exists in concentrations of 200 parts per trillion by weight and 1 part per trillion by moles.[20] Thulium ore occurs most commonly inChina.Australia,Brazil,Greenland,India,Tanzania, and theUnited States also have large reserves of thulium. In 2001, the total world reserves of thulium were approximately 100,000tonnes. Thulium is the least abundantlanthanide on Earth except for the radioactivepromethium.[10]
Thulium is principally extracted frommonazite ores (~0.007% thulium) found in river sands, throughion exchange. Newer ion-exchange and solvent-extraction techniques have led to easier separation of the rare earths, which has yielded much lower costs for thulium production. The principal sources today are the ionadsorption clays of southern China. In these, where about two-thirds of the total rare-earth content is yttrium, thulium is about 0.5% (or about tied withlutetium for rarity).[10]
The metal can be isolated throughreduction of its oxide withlanthanum metal or bycalcium reduction in a closed container. None of thulium's naturalcompounds are commercially important. In 2001, approximately 50 tonnes per year of thulium oxide were produced.[10] In 1996, thulium oxide cost US$20 per gram, and in 2005, 99%-pure thulium metal powder cost US$70 per gram.[11]
Holmium-chromium-thulium triple-dopedyttrium aluminium garnet (Ho:Cr:Tm:YAG, orHo,Cr,Tm:YAG) is an active laser medium material with high efficiency. It lases at 2080 nm in the infrared and is widely used in military applications, medicine, and meteorology. Single-element thulium-doped YAG (Tm:YAG) lasers operate at 2010 nm.[36] The wavelength of thulium-based lasers is very efficient for superficial ablation of tissue, with minimal coagulation depth in air or in water. This makes thulium lasers attractive for laser-based surgery.[37]
Despite its high cost, portable X-ray devices use thulium that has been bombarded with neutrons in anuclear reactor to produce the isotope thulium-170, having a half-life of 128.6 days and five major emission lines of comparable intensity (at 7.4, 51.354, 52.389, 59.4 and 84.253 keV). Theseradioactive sources have a useful life of about one year, as tools in medical and dental diagnosis, as well as to detect defects in inaccessible mechanical and electronic components. Such sources do not need extensive radiation protection – only a small cup of lead.[38]They are among the most popular radiation sources for use inindustrial radiography.[39]Thulium-170 is gaining popularity as an X-ray source for cancer treatment viabrachytherapy (sealed source radiation therapy).[40][41]
The blue fluorescence of Tm-doped calcium sulfate has been used in personal dosimeters for visual monitoring of radiation.[10] Tm-doped halides in which Tm is in its 2+ oxidation state are luminescent materials that are proposed for electric power generating windows based on the principle of aluminescent solar concentrator.[44]
Soluble thulium salts are mildlytoxic, but insoluble thulium salts are completelynontoxic.[10] When injected, thulium can cause degeneration of theliver andspleen and can also causehemoglobin concentration to fluctuate. Liver damage from thulium is more prevalent in malemice than female mice. Despite this, thulium has a low level of toxicity.[45][46]
In humans, thulium occurs in the highest amounts in theliver,kidneys, andbones. Humans typically consume several micrograms of thulium per year. The roots ofplants do not take up thulium, and thedry matter of vegetables usually contains onepart per billion of thulium.[10] Thulium metal has low to moderate toxicity.[47]
^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.
^Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 25: Thef-block metals: lanthanoids and actinoids".Inorganic Chemistry, 3rd Edition. Pearson. p. 864.ISBN978-0-13-175553-6.
^Thermo Fisher Scientific Chemicals, Inc. (28 March 2024)."SAFETY DATA SHEET".fisher scientific. Section: 5. Fire-fighting measures. Retrieved1 June 2024.{{cite web}}: CS1 maint: location (link)
Cleve, P. T. (1879)."Sur deux nouveaux éléments dans l'erbine" [Two new elements in the oxide of erbium].Comptes rendus (in French).89:478–480. Cleve named thulium on p. 480: "Pour le radical de l'oxyde placé entre l'ytterbine et l'erbine, qui est caractérisé par la bandex dans la partie rouge du spectre, je propose la nom dethulium, dérivé de Thulé, le plus ancien nom de la Scandinavie." (For the radical of the oxide located between the oxides of ytterbium and erbium, which is characterized by thex band in the red part of the spectrum, I propose the name of "thulium", [which is] derived fromThule, the oldest name of Scandinavia.)
Cleve, P. T. (1879)."Sur l'erbine" [On the oxide of erbium].Comptes rendus (in French).89:708–709.
Cleve, P. T. (1880)."Sur le thulium" [On thulium].Comptes rendus (in French).91:328–329.
^Krishnamurthy, Devan; Vivian Weinberg; J. Adam M. Cunha; I-Chow Hsu; Jean Pouliot (2011). "Comparison of high–dose rate prostate brachytherapy dose distributions with iridium-192, ytterbium-169, and thulium-170 sources".Brachytherapy.10 (6):461–465.doi:10.1016/j.brachy.2011.01.012.PMID21397569.
^Ayres, D. C. (15 February 2022).Dictionary of environmentally important chemicals. Desmond Hellier (1st ed.). United States: CRC Press. p. 299.ISBN978-1-315-14115-2.OCLC1301431003.
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