Thulium
Thulium (Tm) is a chemical element with atomic number 69. It is a rare earth element belonging to the lanthanide series of the periodic table.
Properties:
- Thulium is a soft, silvery-gray metal that can be cut with a knife.
- It is relatively ductile and malleable.
- The metal tarnishes slowly in air and reacts slowly with cold water.
- Thulium is paramagnetic above 56 K and antiferromagnetic below that temperature.
- It is a strong reducing agent.
- Thulium has a relatively high melting point and boiling point compared to other rare earth elements.
Occurrence:
- Thulium is one of the least abundant of the rare earth elements.
- It is found in small quantities in various minerals, including monazite, xenotime, and euxenite.
- Thulium is typically extracted from these minerals through ion exchange techniques after the minerals have been processed to separate the rare earth elements.
Isotopes:
- Thulium has one stable isotope, 169Tm.
- Several radioactive isotopes are known, with 171Tm being the most stable.
Uses:
- Thulium has relatively few applications.
- 169Tm can be bombarded in a nuclear reactor to produce 170Tm, an artificial radioisotope that emits gamma rays. This isotope has been used in portable X-ray machines, particularly for medical and industrial radiography.
- Thulium is also used in certain ceramic materials and lasers.
- In very small amounts, thulium is used to dope calcium fluoride crystals, which are then used in some solid-state lasers.
History:
- Thulium was discovered in 1879 by Per Teodor Cleve, a Swedish chemist, while working on erbia, a previously identified earth oxide.
- Cleve named it after Thule, the ancient Greek name for Scandinavia.
Precautions:
- Like other rare earth elements, thulium compounds have relatively low toxicity.
- However, dust from thulium metal can be a fire and explosion hazard.
Compounds:
- Thulium forms compounds primarily in the +3 oxidation state.
- Examples include thulium oxide (Tm2O3) and thulium chloride (TmCl3).