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Name Thulium
Atomic Number 69
Atomic Weight 168.93
Symbol Tm
Melting Point ( °C ) 1545 oC, 2813 oF, 1818.15 K
Boiling Point ( °C ) 1950 oC, 3542 oF, 2223.15 K
Density (g/cm3) 9.321 g/cm3
Earth crust (%) 0.007%
Discovery (Year) 1879
Group Lanthanides
Electron configuration [Xe] 4f136s2
Ionization energy (eV) 6.184 eV

Thulium has an atomic number of 69 and is located in the group name of lanthanides being that it has no group/family. Nevertheless, radioactive thulium can be utilized as a power source for portable x-ray machines and is produced by irradiating the element in a nuclear reactor. Thulium may also be utilized to make magnetic ceramic materials found in microwave equipment.


The metal was discovered by Per Teodor Cleve in 1879 and is appeared as a bright, soft, malleable, silvery-gray metal that can be cut with a knife. The element name comes from ‘Thule’, an ancient name for Scandinavia. It is the second rarest lanthanide element, after promethium which is not found in nature, but can be found in a number of minerals. It is one of the least abundant elements that tarnishes when in contact with air and reacts with water. In fact, it is a non-toxic element and poses no threats to plants or animals, however, can become dangerous when it comes to Thulium and its compounds depending on the form. Today, thulium is primarily obtained through an ion exchange process from monazite sand ((Ce, La, Th, Nd, Y)PO4), a material rich in rare earth elements that can contain as much as 0.007% thulium.


1. http://www.livescience.com/38390-thulium.html

2. http://www.rsc.org/periodic-table/element/69/thulium

3. http://education.jlab.org/itselemental/ele069.html

4. http://www.lenntech.com/periodic/elements/tm.htm#Health%20effects%20of%20thulium

5. http://www.chemicool.com/elements/thulium.html

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