Electron Configuration of Thulium (Tm)
Thulium (Tm, Z = 69) has the electron configuration [Xe] 4f^13 6s^2, filling 6 shells with 2, 8, 18, 31, 8, 2 electrons.
Looking for Thulium's electron configuration without wading through a whole chapter? Here is the direct answer first, then the tables and derivations examiners want to see. Every number on this page comes from the same engine that powers the interactive table. Need the whole picture instead — history, characteristics, uses, exam questions? The full Thulium page is one click away.
Thulium: every subshell, one by one
Read the configuration like a receipt: each line is one subshell, and the running total climbs exactly to 69 electrons — never one more, never one less.
| Subshell | Electrons | Total so far |
|---|---|---|
| [Xe] | 0 | 54 |
| 4f | 13 | 67 |
| 6s | 2 | 69 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Thulium carries 2 in shell 1, 8 in shell 2, 18 in shell 3, 31 in shell 4, 8 in shell 5, 2 in shell 6. The outermost shell holds 2 electrons — the ones that do all the bonding.
How to derive it yourself
Follow the aufbau order (1s → 2s → 2p → 3s → 3p → 4s → 3d → …), pouring 69 electrons into orbitals of capacity 2 (s), 6 (p), 10 (d) and 14 (f) until none remain. Write the filled inner shells as the nearest noble-gas core — for Thulium that gives [Xe] 4f^13 6s^2.
Students also ask
How many electron shells does Thulium have?
Thulium is in period 6, so its electrons occupy 6 shells, holding 2, 8, 18, 31, 8, 2 electrons respectively.
How many valence electrons does Thulium have?
Its outermost shell holds 2 electrons, so Thulium has 2 valence electrons that take part in bonding.
What is the noble-gas shorthand for Thulium?
The shorthand form is exactly [Xe] 4f^13 6s^2.