Chemical element · Atomic number 69
Thulium
Thulium in the periodic table: atomic number 69, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Lanthanide
solid
168.93422 u
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Atomic classification
Shell occupancy
Thulium in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 8 electrons
- M · n=3
- 18 electrons
- N · n=4
- 31 electrons
- O · n=5
- 8 electrons
- P · n=6
- 2 electrons
- Electron configuration
- [Xe]6s2 4f13
- Electrons per shell
- 2 · 8 · 18 · 31 · 8 · 2
- Group
- not reported
- Period
- 6
- Block
- F
- Element category
- Lanthanide
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Physical and chemical properties
- Atomic mass
- 168.93422 u
- Standard state
- solid
- Density
- 9.32 g/cm³
- Melting point
- 1,818 K
- Boiling point
- 2,223 K
- Electronegativity
- 1.25 (Pauling)
- First ionisation energy
- 6.184 eV
- Oxidation states
- +3
- Discovery
- 1879
Safety and periodic classification
Safety
Safe handling cannot be inferred from Thulium's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Thulium is in period 6 and the F block. Its direct neighbours by atomic number are Erbium and Ytterbium. The recorded Pauling electronegativity is 1.25. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.