Thulium (Tm): electron configuration, atomic mass and facts
Thulium (Tm) is element 69 of the periodic table, a lanthanide in period 6 (f-block). Its electron configuration is [Xe] 4f13 6s2, with electrons arranged in shells 2, 8, 18, 31, 8, 2, and its standard atomic weight is 168.93 u.
▶ Watch Thulium’s electrons orbit in the interactive periodic tableThulium at a glance
| Symbol | Tm |
|---|---|
| Atomic number | 69 |
| Atomic mass | 168.93 u |
| Category | Lanthanide |
| Group | f-block (no group number) |
| Period | 6 |
| Block | f-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f13 5s2 5p6 6s2 |
| Noble-gas shorthand | [Xe] 4f13 6s2 |
| Electrons per shell | 2, 8, 18, 31, 8, 2 |
| Electronegativity (Pauling) | 1.25 |
| State at 20 °C | solid |
Where is Thulium on the periodic table?
Thulium is in period 6 of the f-block, the lanthanide row printed below the main table. It has 6 electron shells, and this row is where the 4f subshell fills.
How to work out the electron configuration of Thulium
Put 69 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p⁶ (10), 3s² (12), 3p⁶ (18), 4s² (20), 3d¹⁰ (30), 4p⁶ (36), 5s² (38), 4d¹⁰ (48), 5p⁶ (54), 6s² (56), 4f¹³ (69). In shorthand, [Xe] stands for the 54 electrons of xenon, giving [Xe] 4f¹³ 6s².
How electronegative is Thulium?
Thulium has a Pauling electronegativity of 1.25, ranking 74 of the 100 elements with a known value (fluorine is highest at 3.98). That is low: it tends to give up electrons and form positive ions.
Frequently asked questions
What is the electron configuration of Thulium?
The electron configuration of Thulium (Tm) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f13 5s2 5p6 6s2. In noble-gas shorthand it is written [Xe] 4f13 6s2.
How many electrons does Thulium have in each shell?
Thulium has 69 electrons arranged in shells as 2, 8, 18, 31, 8, 2.
What is the atomic mass of Thulium?
The standard atomic weight of Thulium is 168.93 u, so one mole of Thulium atoms has a mass of about 168.93 g.
Is Thulium a metal?
Yes. Thulium is a lanthanide.
Explore nearby elements
More lanthanides: Terbium, Dysprosium, Holmium, Erbium, Ytterbium, Lutetium. See all elements on the periodic table.