Page 35 - Curriculum Visions Dynamic Book

Thulium (Tm)
Element 69. Once thought of as the rarest member of the rare-earth metals (lanthanides) in the Periodic Table, new ores have recently been found and it is now thought of as being about as rare as silver, gold or cadmium.
The metal is silvery coloured, very soft and can be cut with a knife. It
is easily worked. It does not readily corrode in dry air but quickly decomposes in damp air or water.
Discovery
Biology
Thulium is not found in living things. It is regarded as a toxic substance.
Key facts...
Name: thulium
Symbol: Tm
Atomic number: 69
Atomic weight: 168.9
Position in Periodic Table: inner transition metal;
period 6 (lanthanide series)
State at room temperature: solid
Colour: silvery
Density of solid: 9.31 g/cc
Melting point: 1,545°C
Boiling point: 1,727°C
Origin of name: named after Thule, an ancient
word for Scandinavia
Shell pattern of electrons: 2–8–18–31–8–2
Thulium was discovered in Sweden in 1879 by Per Teodor Cleve.
Technology
Thulium has few uses because it is very expensive to isolate.Thulium can be isolated by reduction of the oxide with lanthanum metal. New refining techniques are making it cheaper to extract and therefore a more attractive option for some uses. It is incorporated in some alloys.Artificially radioactive thulium is used in small portable X-ray machines. Isotopes of thulium have potential
as nuclear energy sources and as the ferrites (ceramic magnetic materials) in microwave equipment.
Geology
Thulium is never found as the native metal, but occurs in complex minerals
of gadolinite, monazite sand, and bastnasite.The main economically useful ore is monazite, and even it contains only about 0.007% of the element by volume.
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