hulium is a chemical element with the symbol Tm and atomic
number 69. Thulium is a metal from the group of rare earths. Like other
lanthanides, it is malleable and ductile at room temperature. It oxidizes little
in dry air.
Its name derives from the Greek "Thule", which means "Nordic country". This is
the old name for Scandinavia, where we found gadolinite, an ore in which Per
Theodor Cleve discovered it in 1879, at the same time as holmium.
Originally, the symbol was "You"; thereafter, the agreement was made on "Tm".
It is the rarest of the rare earths (0.007% in the monazite); in the form of
metal, it is much more expensive than gold. Natural thulium is formed
exclusively from the stable isotope 169Tm.
Physical properties
Thulium samples.
Pure thulium is shiny and silvery. It tarnishes when exposed to air. It can be
cut with a knife9 and it is malleable and ductile10: it has a hardness of
between 2 and 3 on the Mohs scale. Thulium is ferromagnetic below 32 K,
antiferromagnetic between 32 K and 56 K and paramagnetic above 56 K11. Liquid
thulium is very volatile12.
Thullium has two main allotropic forms: tetragonal thulium ¦Á-Tm and hexagonal
thulium (most stable) ¦Â-Tm
They are limited due to the high price of this item.
Radiation source: 169Tm compounds "bombarded" with neutrons are used as the
radiation source in portable radiographic devices.
Pigment for cathode ray tube: zinc sulfide doped with thulium oxide (Tm2O3) is
used as a blue phosphor for cathode ray tubes.
Microwave component: magnetic ceramics containing thulium oxide are used in
magnetrons (microwave generator device, used, for example, in microwave ovens).
Heat source, among other things in nuclear batteries composed of the 171Tm
isotope. This has a half-life of 1.92 years.
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rhenium germanium zirconium cadmium hafnium
barium lithium beryllium strontium calcium
Tantalum gadolinium samarium yttrium ytterbium
Lutetium praseodymium holmium erbium thulium dysprosium
terbium europium lanthanum cerium neodymium scandium
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