At A Glance: Tm

Atomic Number: 69
Atomic Symbol: Tm
Atomic Weight: 168.9342
Electron Configuration: [Xe]6s24f13
Atomic Radius: 227 pm (Van der Waals)
Melting Point: 1545 °C
Boiling Point: 1950 °C
Oxidation States: 3, 2
Sources: The element is never found in nature in pure form, but it is found in small quantities in minerals with other rare earths.Uses: Because of the relatively high price of the metal, thulium has not yet found many practical applications.Content provided by Los Alamos National Laboratory. Used with permission.

Rare earth element - Thulium
Rare earth element - Thulium
Thulium Spin Video

Photos of rare earth elements used on our site are copyright of Max Whitby and Theodore Gray. Used with permission.

Because of the relatively high price of the metal, thulium has not yet found many practical applications. 169Tm bombarded in a nuclear reactor can be used as a radiation source in portable X-ray equipment. 171Tm is potentially useful as an energy source. Natural thulium also has possible use in ferrites (ceramic magnetic materials) used in microwave equipment, and can be used for doping fiber lasers. As with other lanthanides, thulium has a low-to-moderate acute toxic rating. It should be handled with care.


Named after Thule, the earliest name for Scandinavia. Discovered in 1879 by Cleve. Thulium occurs in small quantities along with other rare earths in a number of minerals. It is obtained commercially from monazite, which contains about 0.007% of the element. Thulium is the least abundant of the rare earth elements, but with new sources recently discovered, it is now considered to be about as rare as silver, gold, or cadmium.


Thulium can be isolated by reduction of the oxide with lanthanum metal or by calcium reduction of a closed container. The element is silver-gray, soft, malleable, and ductile, and can be cut with a knife. Twenty five isotopes are known, with atomic masses ranging from 152 to 176. Natural thulium, which is 100% 169Tm, is stable.

Source: Los Alamos National Laboratory

Comments are closed.