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For lasers.
Atomic Number:69Atomic Symbol:Tm
Atomic Weight:168.9342Electron Configuration:2-8-31-8-2
Shells:2,8,18,31,8,2Filling Orbital:4f13
Melting Point:1545oCBoiling Point:1727oC
Description:Silver colored rare earth metal.
Uses:Radioactive thulium is used to power portable x-ray machines,
eliminating the need for electrical equipment


(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.
  • Ion-exchange and solvent extraction techniques have recently permitted much easier separation of the rare earths, with much lower costs.


  • 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.


  • 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.


Only a few years ago, thulium metal was not obtainable at any cost; in 1985 the oxide sold for $3400/kg. Thulium metal costs $50/g.


As with other lanthanides, thulium has a low-to-moderate acute toxic rating. It should be handled with care.

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