Electron Configuration of Terbium (Tb)
Terbium (Tb, Z = 65) has the electron configuration [Xe] 4f^9 6s^2, filling 6 shells with 2, 8, 18, 27, 8, 2 electrons.
Teachers call it "one fact, fully handled" — exactly what this page does for Terbium. The answer sits at the top in bold; scroll for the working, the shell-by-shell breakdown and the two questions students ask most. Need the whole picture instead — history, characteristics, uses, exam questions? The full Terbium page is one click away.
Terbium: every subshell, one by one
Start from 1s and follow the running total: this is exactly how examiners expect you to build Terbium's configuration on paper.
| Subshell | Electrons | Total so far |
|---|---|---|
| [Xe] | 0 | 54 |
| 4f | 9 | 63 |
| 6s | 2 | 65 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Terbium carries 2 in shell 1, 8 in shell 2, 18 in shell 3, 27 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 65 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 Terbium that gives [Xe] 4f^9 6s^2.
Students also ask
How many electron shells does Terbium have?
Terbium is in period 6, so its electrons occupy 6 shells, holding 2, 8, 18, 27, 8, 2 electrons respectively.
How many valence electrons does Terbium have?
Its outermost shell holds 2 electrons, so Terbium has 2 valence electrons that take part in bonding.
What is the noble-gas shorthand for Terbium?
The shorthand form is exactly [Xe] 4f^9 6s^2.