69TmThulium168.934222[Xe] 4f¹³ 6s²
lanthanide
Thulium
Thulium is a chemical element with symbol Tm and atomic number 69. It is the thirteenth and antepenultimate (third-last) element in the lanthanide series. Like the other lanthanides, the most common oxidation state is +3, seen in its oxide, halides and other compounds.
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
Electrons by shell
Electron configuration
4f13
6s2
54 is the [Xe] core total across five shells.
At a glance
- Atomic number
- 69
- Atomic mass
- 168.934222 u
- Phase
- Solid
- Density
- 9.32 g/cm³
- Melting point
- 1,818 K
- Boiling point
- 2,223 K
- First ionization energy
- 596.7 kJ/mol
- Electronegativity
- 1.25
- Electron affinity
- 99 kJ/mol
- Molar heat capacity
- 27.03 J/(mol·K)
- Period
- 6
- Appearance
- silvery gray
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.