툴륨 (Tm)

발견 과정

발견: 1879 · Per Teodor Cleve

Thulium was discovered by Swedish chemist Per Teodor Cleve in 1879 by looking for impurities in the oxides of other rare earth elements. This was the same method Carl Gustaf Mosander earlier used to discover some other rare earth elements. Cleve started by removing all of the known contaminants of erbia (Er2O3). Upon additional processing, he obtained two new substances; one brown and one green. The brown substance was the oxide of the element holmium and was named holmia by Cleve, and the green substance was the oxide of an unknown element. Cleve named the oxide thulia and its element thulium after Thule, an Ancient Greek place name associated with Scandinavia or Iceland. Thulium's atomic symbol was initially Tu, but later changed to Tm to avoid confusion with tungsten which was commonly written as Tu around the time of thulium's discovery. Thulium was so rare that none of the early wor

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The element is never found in nature in pure form, but it is found in small quantities in minerals with other rare earths. Thulium is often found with minerals containing yttrium and gadolinium. In particular, thulium occurs in the mineral gadolinite. Like many other lanthanides, thulium also occurs in the minerals monazite, xenotime, and euxenite. Thulium has not been found in prevalence over the other rare earths in any mineral yet. Its abundance in the Earth's crust is 0.5 mg/kg by weight. Thulium makes up approximately 0.5 parts per million of soil, although this value can range from 0.4 to 0.8 parts per million. Thulium makes up 250 parts per quadrillion of seawater. In the Solar System, thulium exists in concentrations of 200 parts per trillion by weight and 1 part per trillion by moles. Thulium ore occurs most commonly in China. Australia, Brazil, Greenland, India, Tanzania, and t

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Natural thulium consists of the single observationally stable isotope thulium-169, which is predicted to undergo alpha decay to holmium-165 with a very long half-life. Known isotopes of thulium range from 144Tm to 183Tm. The primary decay mode before the stable isotope, 169Tm, is electron capture to erbium isotopes, and the primary mode after is beta emission to ytterbium isotopes. The longest-lived radioisotopes are thulium-171, which has a half-life of 1.92 years, and thulium-170, which has a half-life of 128.6 days. Most other isotopes have half-lives under 10 minutes.