TM Element Information
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Thulium Element
Thulium is a moderately hard,
silvery white metal that is stable in air but can easily be dissolved in
diluted acids—except hydrofluoric acid (HF), in which an insoluble trifluoride
(TmF3) layer forms on the surface of the metal, impeding further chemical
reaction. Thulium is a strong paramagnet above 56 K (−217 °C, or −359 °F).
Between 56 and 32 K (−241 °C, or −402 °F) the metal is antiferromagnetic with a
sinusoidally modulated magnetic structure along the c-axis of its crystal
structure, and below 32 K thulium is ferrimagnetic.
The element was discovered in
1842 as an oxide by Carl Gustaf Mosander, who originally called it terbia; in
the confusion arising from the similarity in the properties of the rare-earth
elements, the names of two, terbium and erbium, became interchanged (c. 1860).
The element occurs in many rare-earth minerals; among the more important are
the laterite ionic clays, xenotime, and euxenite. Erbium also occurs in the
products of nuclear fission. In Earth’s crust, erbium is as abundant as
tantalum and tungsten.
Natural erbium is a mixture of
six stable isotopes: erbium-166 (33.5 percent), erbium-168 (26.98 percent),
erbium-167 (22.87 percent), erbium-170 (14.91 percent), erbium-164 (1.6
percent), and erbium-162 (0.14 percent). Not counting nuclear isomers, a total
of 30 radioactive isotopes of erbium are known. Their mass varies from 142 to
177. All the radioactive isotopes of erbium are relatively unstable: their
half-lives range from 1 second (erbium-145) to 9.4 days (erbium-169).
Thulium was discovered in 1879,
along with holmium, by Per Teodor Cleve, who named the oxide thulia after an
ancient name for Scandinavia. It is found in small amounts in such rare-earth
minerals as laterite ionic clays, xenotime, and euxenite and in products of
nuclear fission. Thulium is one of the rarest of the rare-earth elements. Its
abundance in Earth’s crust is nearly the same as those of antimony and iodine.
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