Thulium

Thulium is a soft, silvery chemical element with atomic number 69 and symbol Tm. It is a rare-earth metal used in solid-state lasers and compact radiation sources.

Thulium laser: A laser that uses thulium ions as its active medium, commonly emitting near 2 micrometers. Thulium ions produce infrared light useful in surgery and materials processing.
Lanthanide contraction: The gradual decrease in atomic and ionic radii across the lanthanide series as nuclear charge increases. It helps explain thulium’s size and similarities to neighboring rare-earth metals.
Per Teodor Cleve: A Swedish chemist who discovered several rare-earth elements through analysis of mineral fractions. Cleve identified thulium in 1879 while examining erbia fractions.
Erbium: A silvery lanthanide element with atomic number 68, used in fiber optics and lasers. Erbium immediately precedes thulium and shares its trivalent chemistry.
Thulium-170: A radioactive thulium isotope that emits beta particles and characteristic X-rays. Its radiation enables compact, isotope-powered X-ray sources.
Thulium(III): The common oxidation state of thulium, in which the atom has lost three electrons. Most thulium compounds and many of its optical properties involve this ion.
Erbia: The historical name for an oxide-rich fraction containing erbium and other rare-earth elements. Thulium was first detected in material separated from erbia.
Ytterbium: A soft, silvery lanthanide element with atomic number 70, used in lasers and specialty alloys. Ytterbium follows thulium and is more abundant in Earth’s crust.
Portable X-ray generator: A compact device that produces X-rays for imaging outside fixed radiology installations. Thulium-170 can supply X-rays without a conventional electrically powered tube.
4f orbital: An atomic orbital type occupied by electrons in the inner f subshell of lanthanide atoms. Thulium’s partially filled 4f shell gives its ions characteristic optical transitions.

Linked from 3 pages