Discovery date : 1879
Discovered by: Per Teodor Cleve
Origin of the name: The name comes from Thule, the ancient name for Scandinavia.
Allotropes :
~>THULIUM is a chemical element with symbol Tm and atomic number 69. It is the thirteenth and third-last element in the lanthanide series.
| FACT BOX | |||
| Group | Lanthanides | Melting point | 1545°C, 2813°F, 1818 K |
| Period | 6 | Boiling point | 1950°C, 3542°F, 2223 K |
| Block | f | Density (g cm−3) | 9.32 |
| Atomic number | 69 | Relative atomic mass | 168.934 |
| State at 20°C | Solid | Key isotopes | 169Tm |
| Electron configuration | [Xe] 4f136s2 | CAS number | 7440-30-4 |
| ChemSpider ID | 22400 | ChemSpider is a free chemical structure database | |
Thulium was first isolated in 1879 as its oxide by Per Teodor Cleve at the University of Uppsala, Sweden. The discoveries of the many rare earth elements (aka lanthanoid) began with yttrium in 1794. This was contaminated with these chemically similar elements. Indeed the early chemists were unaware they were there. In 1843, erbium and terbium were extracted from yttrium, and then, in 1874, Cleve looked more closely at erbium and realised that it must contain yet other elements because he observed that its atomic weight varied slightly depending on the source from which it came. He extracted thulium from it in 1879.
In 1911, the American chemist Theodore William Richards performed 15,000 recrystallisations of thulium bromate in order to obtain an absolutley pure sample of the element and so determine exactly its atomic weight.