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< 68 69 Tm Thulium 70 >
     
68
Er
167.3
69
Tm
168.9
70
Yb
173.0
100
Fm*
253
101
Md*
256
102
No*
254
Atomic Number: 69
Atomic Radius: 174.6 pm
Atomic Symbol: Tm
Melting Point: 1545 șC
Atomic Weight: 168.9342
Boiling Point: 1950 șC
Electron Configuration: [Xe]6s24f13
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History

(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.

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, 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.

Costs

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


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