Thulium (Tm) – element 69
Thulium is a chemical element with the symbol Tm and atomic number 69. It is a lanthanide in group 3 (lanthanides), period 6 of the periodic table (f-block), and is a solid at room temperature.
Thulium (Tm) has atomic number 69, atomic mass 168.93 u and electron configuration [Xe] 4f13 6s2.
Thulium facts
| Symbol | Tm |
|---|---|
| Atomic number | 69 |
| Atomic mass | 168.93 u (g/mol) |
| Category | lanthanide |
| Group | group 3 (lanthanides) |
| Period | 6 |
| Block | f-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f13 |
| Noble-gas notation | [Xe] 4f13 6s2 |
| Electrons per shell | 2, 8, 18, 31, 8, 2 |
Bohr model and shells
Thulium has 69 electrons in 6 shells: 2, 8, 18, 31, 8, 2. Full configuration and noble-gas notation are in the table; work out any element or ion with the electron configuration calculator.
Physical and atomic properties
| Melting point | 1818 K (1544.8 °C) |
|---|---|
| Boiling point | 2223 K (1949.8 °C) |
| Density | 9.32 g/cm³ |
| Electronegativity (Pauling) | 1.25 |
| Electron affinity | 99 kJ/mol |
| Ionization energies | 596.7, 1160, 2285 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 27.03 J/(mol·K) |
| Discovered by | Per Teodor Cleve |
Use the atomic mass in the molar mass calculator for any formula containing Tm.
Position in the periodic table
Tap any element to open its page.
Frequently asked questions
What is the atomic mass of thulium?
The atomic mass of thulium is 168.93 u, so one mole of thulium atoms weighs 168.93 g.
What is the electron configuration of thulium?
Thulium has 69 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹³, or [Xe] 4f¹³ 6s² in noble-gas notation. Electrons per shell: 2, 8, 18, 31, 8, 2.
Is thulium a metal?
Yes. Thulium is a lanthanide.
Where is thulium on the periodic table?
Thulium is in group 3 (lanthanides), period 6, in the f-block.
Data: Periodic-Table-JSON (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.