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
Documented element sampleA documented sample of elemental thulium; the rare earth metal appears silvery-gray.
Image credit: James St. John
Auto-oriented, limited to 1600 × 1200 pixels and re-encoded as WebP; the subject was not altered.
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
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.
Where Thulium sits among the 118 elements
The table compares the reported values for Thulium with every other element that carries the same value in the snapshot. A rank is not a judgement, it is orientation: it says how unusual this value is across the periodic table.
| Value | Thulium | Position in the data set |
|---|---|---|
| Melting point | 1,818 K | Rank 24 of 103 elements with a reported value. Highest: Carbon. |
| Boiling point | 2,223 K | Rank 54 of 93 elements with a reported value. Highest: Rhenium. |
| Density | 9.32 g/cm³ | Rank 29 of 96 elements with a reported value. Highest: Osmium. |
| Electronegativity (Pauling) | 1.25 | Rank 74 of 95 elements with a reported value. Highest: Fluorine. |
| Ionisation energy | 6.184 eV | Rank 69 of 102 elements with a reported value. Highest: Helium. |
All values and ranks come from the PubChem Periodic Table snapshot, retrieved on 2026-07-15. Elements without a reported value are excluded, so the population differs per row.
The neighbours of Thulium in the periodic table
- Place in the table
- No group number, period 6, F block. Classified as lanthanide, solid at standard conditions.
- Direct neighbours
- Atomic number 69. Preceded by Erbium, followed by Ytterbium.
- Discovery
- Recorded in the snapshot as: 1879. Who, where and under what circumstances is not part of that record, so this page carries the sourced year and no discovery narrative.
- Oxidation states
- +3. They follow from the electron configuration [Xe]6s2 4f13 and indicate which compounds to expect.
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