What is Thulium

Thulium (pronounced as Thoo-lee-em) ^[2] is a soft, silver-gray rare earth metal ^[3] belonging to the Lanthanides group and represented by the symbol Tm ^[1]. While its most abundant, naturally occurring isotope is ¹⁶⁹Tm, it has 34 radioactive isotopes, out of which the most stable one is ¹⁷¹Tm with a half-life period of 1.92 years ^[4].

Where is it Found

Thulium is found in small quantities in monazite, a mineral that has approximately 20 parts per million (ppm) of the metal in the earth’s crust ^[1]. It is then commercially extracted through ion-exchange and solvent-extraction processes ^[1]. The element can as well be isolated through calcium reduction of anhydrous fluoride or by reduction of oxide with lanthanum ^[1]. While the top 3 thulium producing nations are China, Russia, and Malaysia, the top 3 thulium reserve holders are China, CIS Countries, and Russia ^[1].

History

Origin of its Name: It is named after Thule, the ancient name that stood for the present-day Scandinavia ^{[1, 2]}.

Who discovered it: The Swedish chemist Per Teodor Cleve is credited for the discovery of thulium ^[1].

When and How was it discovered

Men started finding the lanthanoids or rare earth elements in 1794 when yttrium was found by Johan Gadolin ^[1]. Later, the chemists analyzed the composition of yttrium and observed that it was contaminated with chemically similar elements ^[1]. As a result, two new elements terbium and erbium were isolated in 1843 ^[1].

Per Teodor Cleve started working on erbium in 1874 and was able to successfully isolate thulium in its oxide form in 1879 at the Uppsala University, Sweden ^{[1, 5]}. In 1911, the exact atomic weight of thulium was determined by Theodore William Richards, an American chemist who carried out 15,000 thulium bromate-recrystallizations to produce the pure form of thulium ^[1].

Thulium Identification
Atomic number	69 [1]
CAS number	7440-30-4 [1]
Position in the periodic table	Group	Period	Block
	Lanthanides [1]	6 [1]	f [1]

Properties and Characteristics of Thulium

Atomic Data of Thulium (Element 69)

What is Thulium used for

• Thulium-170 (¹⁷⁰Tm), a radioactive isotope formed by bombarding thulium in a nuclear reactor, can be used as a portable source of radiation in medical x-ray machines ^{[1, 7]}.
• The element 69 is used as a dopant in fiber lasers for surgical applications ^{[1, 3]}.
• Since it emits a bluish glow when exposed to ultra-violet light, thulium is used in Euro banknotes for detecting counterfeit currency ^[5].
• It can also be used with other lanthanides for producing alloys ^[5].

Possible Harmful Effects or Toxicity

Being a non-toxic element, it does not cause any health hazards ^[1].

Interesting Facts

• Because of its softness and malleability, thulium can be easily cut with a knife ^[3].
• The element is sometimes represented by an image of a snow-covered mountain to indicate the origin of its name, suggesting a region far off to the north ^[1].

Cost of Thulium

While one gram of thulium costs about $50 ^[8], a hundred gram of the element approximately costs $500-$700 ^{[5, 8]}.

References
1. http://www.rsc.org/periodic-table/element/69/thulium
2. https://education.jlab.org/itselemental/ele069.html
3. https://www.livescience.com/38390-thulium.html
4. https://www.webelements.com/thulium/isotopes.html
5. https://www.chemicool.com/elements/thulium.html
6. http://periodictable.com/Elements/069/data.html
7. https://applets.kcvs.ca/IPTEI/pdf-elements/thulium.pdf
8. https://www.radiochemistry.org/periodictable/elements/69.html