Introducing Thulium: Element Number 69
Thulium, designated by the chemical symbol Tm and having an atomic number of 69, is a fascinating member of the lanthanide series within the periodic table. It is classified as a rare earth element, meaning it is not rare in the sense of being scarce in the Earth’s crust, but rather that it is typically dispersed and not found in large, concentrated deposits. This silvery-grey metal is known for being soft enough to be cut with a knife and is both malleable (can be hammered into thin sheets) and ductile (can be drawn into thin wires). Despite its metallic properties, thulium readily tarnishes in moist air and reacts slowly with cold water.
Discovery and Naming
Thulium was discovered in 1879 by Per Teodor Cleve, a Swedish chemist. Cleve made this discovery while analyzing the mineral erbia. He used a series of separation techniques to isolate new substances from the impure erbia, eventually identifying two distinct oxides, which he named holmia and thulia. The metallic element isolated from thulia was then named thulium.
The name “Thulium” is derived from “Thule,” an ancient Greek and Roman name for a mythical land generally believed to be the northernmost part of the world, often associated with Scandinavia or Iceland. Cleve, being Swedish, chose this name in reference to his homeland in the far north of Europe.
Quick Facts About Thulium
- Rarity among Rare Earths: Thulium is the second least abundant of the lanthanide elements found in the Earth’s crust, with promethium being the least abundant (and primarily man-made).
- Medical Applications: One significant use of thulium is in portable X-ray devices. The isotope Thulium-170 is utilized in these compact machines, providing a convenient way to perform radiographic examinations in remote locations or emergency situations worldwide, where traditional X-ray equipment might not be available.
- Laser Technology: Thulium-doped fiber lasers are employed in various applications, including medical surgery and industrial cutting. These lasers emit light in the infrared spectrum, which has specific advantages for certain procedures.
- Magnetic Materials: Thulium can be used in specialized ceramic magnetic materials known as ferrites. These materials have applications in microwave equipment and computer memory devices.
- Occurrence: Thulium is never found as a free element in nature. Instead, it is always found in combination with other rare earth elements in minerals such as monazite and bastnäsite. These minerals are mined in various locations globally, including China, the United States, and Australia.