Thulium
Atomic Number:
69
Atomic Symbol:
Tm
Atomic Weight:
168.9342
Electron Configuration:
2-8-31-8-2
Shells:
2,8,18,31,8,2
Filling Orbital:
4f13
Melting Point:
1545oC
Boiling 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.
History
(Thule, the earliest name for Scandinavia) Discovered in 1879 by Cleve.
Occurence
• 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.
Properties
• 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.
Uses
• 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.
Costs
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.
Handling
As with other lanthanides, thulium has a low-to-moderate acute toxic rating. It should be handled with care.
