Element 69
Thulium (Tm)
Thulium (Tm) is element 69 of the periodic table, a lanthanide in period 6 (f-block) with an atomic mass of 168.93 and is a solid at standard conditions.
At a glance
- Atomic number
- 69
- Symbol
- Tm
- Atomic mass
- 168.93 u
- Category
- Lanthanides
- Period
- 6
- Block
- f-block
- Phase at STP
- solid
Electron structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f13 5s2 5p6 6s2
- Shorthand configuration
- [Xe] 4f13 6s2
- Electrons per shell
- 2, 8, 18, 31, 8, 2
- Oxidation states
- +2, +3
Physical properties
- Melting point
- 1818 K
- Boiling point
- 2223 K
- Density
- 9.321 g/cm3
- Phase
- solid
Atomic properties
- Electronegativity (Pauling)
- 1.25
- Atomic radius
- 222 pm
- Covalent radius
- 190 pm
- First ionization energy
- 597 kJ/mol
- Electron affinity
- 50 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| Tm-169 | 168.93422 | 100% | Stable |
Common uses
- Portable X-ray devices
- Lasers
- Superconductors
- Ceramics
Discovery
- Year
- 1879
- Discovered by
- Per Teodor Cleve
- Country
- Sweden