|Boiling Point: 2220°K, 1947°C, 3537°F
Melting Point: 1818°K, 1545°C, 2813°F
Electrons Energy Level: 2, 8, 18, 31, 8, 2
Isotopes: 34 + 1 Stable + 14 meta states
Heat of Vaporization: 191 kJ/mol
Heat of Fusion: 16.84 kJ/mol
Density: 9.32 g/cm3 @ 300°K
Specific Heat: 0.16 J/g°K
Atomic Radius: 2.42Å
Ionic Radius: 0.869Å
Electronegativity: 1.25 (Pauling); 1.11 (Allrod Rochow)
Vapor Pressure: 0.0049 Pa @ 1545°C
1s2 2s2p6 3s2p6d10 4s2p6d10f13 5s2p6 6s2
The rarest of the naturally-occurring rare-earth metals, thulium was discovered by Swedish chemist Per Teodor Cleve in 1879 by looking for impurities in samples of erbia, an oxide of erbium (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) and upon additional processing, obtained two new substances; one brown and one green. The brown substance turned out to be the oxide of the element holmium and was named holmia. The green substance was the oxide of an unknown element. Cleve named the oxide thulia and its element thulium for the ancient name for Scandinavia, Thule.
Like others in the lanthanide series, thulium is silver in color but it is also very soft---soft enough to cut with a knife. Thulium is the least abundant of the naturally occurring rare earth elements.
The element is never found in nature in pure form, but it is found in small quantities in minerals with other rare earths. It is principally extracted from monazite (~0.007% thulium) ores found in river sands through ion-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 metal can be isolated through reduction of its oxide with lanthanum metal or by calcium reduction in a closed container. None of thulium's compounds are commercially important.
Thulium has been used to create lasers but high production costs have prevented other commercial uses from being developed. Other applications, real and potential, include:
Metallic thulium is relatively expensive and has only recently become available. It currently has no commercial applications.
Thulium forms no commercially important compounds. Some of thulium's compounds include: thulium oxide (Tm2O3), thulium fluoride (TmF3) and thulium iodide (TmI3).
Naturally occurring thulium is composed of 1 stable isotope, 169Tm (100% natural abundance. 34 radioisotopes have been characterized, with the most stable being 171Tm with a half-life of 1.92 years, 170Tm with a half-life of 128.6 days, 168Tm with a half-life of 93.1 days, and 167Tm with a half-life of 9.25 days. All of the remaining radioactive isotopes have half-lifes that are less than 64 hours, and the majority of these have half lifes that are less than 2 minutes. This element also has 14 meta states, with the most stable being Tm-164m (t½ 5.1 minutes), Tm-160m (t½ 74.5 seconds) and Tm-155m (t½ 45 seconds).
The isotopes of thulium range in atomic weight from 144.97007 amu (145Tm) to 178.95534 amu (179Tm). The primary decay mode before the most abundant stable isotope, 169Tm, is electron capture, and the primary mode after is beta emission. The primary decay products before 169Tm are element erbium-68 isotopes, and the primary products after are element ytterbium-70 isotopes.
Thulium has a low-to-moderate acute toxic rating and should be handled with care. Metallic thulium in dust form presents a fire and explosion hazard.
Atomic Radius (Å): 2.42Å
Electrochemical Equivalents: 2.101g/amp-hr
Atomic Mass Average: 168.9342