Thulium

Thulium Details

Thulium Symbol: Tm

Thulium Atomic Number: 69

Thulium Atomic Weight: 168.934

What is Thulium?

Thulium (atomic number 69, symbol Tm) is a rare earth metal and chemical element that was isolated in 1879 by Per Theodor Cleve. The same method was used to isolate other elements, including terbium, erbium, and lanthanum. It was only in 1911 when pure thulium was isolated. This is a rare and expensive element which belongs to the group of lanthanides.

Properties, Compounds, and Isotopes
Thulium is ductile and malleable and has a silver luster. It has a hexagonal close-packed structure and three oxidation states - 4, 3, and 2. This element is solid at room temperature and has a boiling point of 3536 F (1947 °C) and melting point of 2813 °F (1545 °C). It is volatile in liquid form and tarnishes when exposed to water or air. The ionic and Vanderwaals radius of thulium are unknown. Tm-169 is the isotope with the longest half life. There are 5 stable isotopes – Tm-171, Tm-170, Tm-169, Tm-178, and Tm-167. The element reacts with hydrogen chloride, halogens, metals, and nonmetals and forms compounds such as trimedoxine bromide, thulium nutride, and others. Chalcogenides are formed when thulium reacts with chalcogens such as astatine, iodine, bromine, chlorine, and fluorine. These elements have similar chemical properties. The compounds are yellow or white in color. Thulium hydroxide and hydrogen gas are formed when water reacts with thulium dichloride. The only oxide is thulium oxide powder.

Occurrence, Estimated Reserves, and Extraction Techniques
Thulium is found in countries such as the United States, Tanzania, India, Greenland, Brazil, and Australia. The main deposits are in China.

Major reserve holders also include the Commonwealth of Independent States and the U.S. Top producers include Brazil, Russia, and China. The total reserves are estimated at 100,000 tonnes. The element is not found in nature and occurs in minerals that contain gadolinium and yttrium. It is also found in minerals such as euxenite, xenotime, monazite, and gadolinite. The main methods of extraction include solvent extraction and ion exchange. Calcium reduction is also used.

Commercial Applications
Thulium has several applications in meteorology and medicine and is used in X-ray devices, radiation dosimeters, and lasers. X-ray devices that contain thulium are lightweight and portable. One of its isotopes, Tm-170 is used in brachytherapy. Also known as endocurietherapy and curietherapy, it is used to treat skin, breast, prostate, and other types of cancer. Brachytherapy is also used together with other treatments such as chemotherapy and external beam radiotherapy and to treat tumors. None of its compounds is commercially important, however. Given that thulium is expensive, it is most often used for research purposes. The element is added to arc lighting and high-temperature superconductors.

Health and Environmental Effects
While thulium is found in the human body, it has no biological role. Soluble salts, have been found to speed metabolism. Insoluble salts are non-toxic and safe while soluble ones are slightly toxic. The element poses no threat to plant and animal life and is thus not considered environmental hazard.

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